In short, Communion becomes our stand-in for magic, and it allows us the power of enchantment. Not direct enchantment, of course. Neither Star Wars nor Psi-Wars has the patience for mystics standing over an item chanting for days on end. Both of them favor diving deep into ancient tombs and long-dead spaceship to find some ancient relic of power. The following rules discuss how to handle those.
Enchantment through Age
If we're going to treat these like magic items, then we need to use magic-item rules to cover it, and the closest to what I have in mind is Enchanment Through Age, found in GURPS Thaumatology, starting on page 110.
Mechanisms of Enchanment
Enchantment Through Age requires a mechanism and proposes three:
- Amplification (that is, places of power or certain circumstances can imbue the item with power),
- Significance (The item has a great deal of legend and story around it)
- Use (that the item was regularly used for a particular thing.
For our purposes, Significance is by far the most important. An item must be legendary, impressive and noteworthy, otherwise Communion would fail to interact with it and it would gain no powers. The other two are less important. They might, perhaps, speed up the process or take on a secondary role. For example a forgotten force blade with no legend associated with it, used to murder the crew of a dead ship, and then left there for hundreds of years, might accrue some power from the local emotion and fear and the deathly energies in the ship, but we wouldn't expect it to be as powerful as the First Emperor's force blade.
Rate of Enchantment
How quickly does an item gain power? The book suggests values somewhere between 10 energy points per year, and 1 per 10 years. It also points out that we can assign character points rather than energy points, using a 25 to 1 exchange rate, which we're going to use. The Relics of Communion are psychotronic in nature. They'll use the Psychotronics rules (especially when it comes to assigning a dollar cost!).
A rate of 5 energy points in a year would give you 1 character point in 5 years, which means someone wielding an item of some significance could get a quick in a relatively recent amount of time. It means that over the course of a generation, a relic could acquire 5 character points, which is sufficient for a decent advantage. Over 100 years, our relic would be up to 20 points, and over 1000 years, an item would reach up to 200 points.
Using the Psychotronic rules this means that a small (easily hand-held) item would gain about $500 a year in value/enchantment. However, note that Communion-based psychotronics should always be self-powered, increasing the cost by 1.5, so they gain $750 a year.
Obviously, nearly any Psionic Power (including quite a few of the "forbidden" ones, especially from Probability Manipulation) and most Communion powers will work. Note that if it is "enchanted by age," it was empowered by Communion, and is thus Divine, and associated with one of the three forms of communion (This explicitly means you should apply the Divine limitation: relics of Ego communion only work for the worthy, relics of Dark Communion fail against those of Ego communion and relics of Broken Communion inflict some form of Corruption) and is affected by Sanctity levels.
Some generally useful advantages do apply, though. First, just as characters can have Destiny, so can relics. The destiny is specific to the relic (ie "This force blade is destined to slay kings"), but while helping that item fulfill its destiny, you may use its impulse buy points as normal. Second, consider giving items a Higher Purpose. This catch-all allows for items that grant a bonus when doing something specific, such as killing robots or protecting the innocent, etc. Third, consider granting items a Legendary Reputation. The force blade of a famous Righteous Crusader (they're never referred to that way, of course. The Righteous Crusader is always a specific person, like "Luke Skywalker" or "Dun Beltain", but his legend falls into the particular path, so the Force Blade of Dun Beltain might have a Legendary Reputation for the Righteous Crusader). This grants the normal bonus to Divine Reaction rolls when used, and stacks with the character's own Legendary Reputation, to a maximum of +4. It is not sufficient to fulfill the prerequisite for purchasing learned prayers.
Acquiring and Using Relics
Relics have sufficient reputation, legend and rarity that it seems crass, and not particularly in keeping with the genre, to treat them as something disposable. That is, a millionaire should not be swimming in relics or, at least, not for long.
I've chosen to apply $ costs, rather than character point costs, because in most GURPS Ultra-Tech games, dollars trump character points when it comes to value. That is, you're better off with piles of money and some skills associated with your tech, than you are with spending those same points on, say, an innate attack that does much the same way. Thus, it seems fitting that players also have a way of buying their cool powers with dollars.
But that said, a rich guy shouldn't have a belt full of magical force swords that he gets to pick from. Communion would likely work against such a character, as such items were meant to breath and fulfill their destiny, or to soak in more communion and legend. Thus, I propose that all relics be purchased as Signature Gear, which automatically ties their legend to that of the hero, or that the character tries to behave in a manner appropriate to the relic, or that the relic be put under lock and key lest Communion find a way to wrest it from you. Thus, all relics should be deeply bound to a character, or temporary but appropriate for his actions, or carefully hidden away awaiting a heist by a more appropriate character, or swiftly lost to someone more appropriate.
Relics, of course, do not use Electronics (Psychotronics), as they're a very different breed of item. Instead, they use either Meditation (if their power requires Will or Focus) or Philosophy (if their power requires IQ or a deeper understanding of Communion). Roll IQ-6, Connoissuer (Relics), or Hidden Lore (Communion) to identify a relic. You may use Expert Skill (Psionics), Psychology, History, Literature, or Archaeology as complimentary skills. Archaeology can, of course, be used for recovering artifacts. Research, History, Literature and Archaeology can all tell you where a specific artifact might currently reside, and Archaeology can be rolled to handle or recover a relic without damaging it.
Sample Relics of Communion
If you need inspiration, just dig through Star Wars lore, or hunt up some books full of enchanted items. There should be plenty of ideas.
The Force Blade of Vesper Tane
|the starkiller v3 lightsaber by tyrapollo|
Associated Communion: Dark Communion (the Rebellious Beast)
Statistics: TK-Tether 
Notorious rebel and outlaw Vesper Tane hand-crafted this force blade, and it knows him. It psychokinetically flies to its master as a free action. Vesper Tane has, of course, vanished mysteriously, but his force blade still seeks him, and it will happily fly to the grip of someone else that it feels matches Vespers savage charisma, or that will get it one step closer to its missing master.
The Lost Forceblade of the Fallen Alexian Dynasty
|just my lightsaber by phelandavion|
Associated Communion: Communion (The Righteous Crusader)
Statistics: Destiny 2 (Restore the Alexian Dynasty) , Legendary Reputation (Righteous Crusader) +1 
Discovered by Dun Beltain on an old Alexian warship that was being salvaged by his homeworld of Grist, he has long carried them, and only recently become aware of their power, their connection to a lost destiny, and the legend of their owner, a fallen protector of the last known princess of that dynasty. To fully unlock their powers, he needs to discover more about them.
Severance, the Dark Blade
|elder lightsaber by squint911|
Associated Communion: Broken Communion (Death)
Statistics: Neutralize (Psi, Cosmic, also affects Anti-Psi +50%, Cosmic, no rule of 16 +50%; Reliable +8 (For Crippling Only -50%) +30%, Always On -20%, Crippling Only -50%, Contact Agent -30%, Broken Communion -20%) 
This ancient relic from a bygone era (it's at least 500 years old) has been infused with the power of Deathly Broken Communion. The moment the blade touches the flesh of a psychic (or an anti-psi!), the wielder and the target must engage in a contest of wills. If the wielder succeeds, the target is not only injured by the blade, but one full psionic power is crippled. Each such use (which are non-optional if the blade impacts the target) inflicts 10 points of death-associated corruption on the user.
The Alexian Royal Pendant
|nims pendant by aikurisu|
Associated Communion: Communion (the Bound Princess)
Statistics: Aspect 4 , Avatar , Intimidation Factor 
One of the other lost treasures of the fallen Alexian dynasty, the worthy wearer of this immediately gains a regal aspect equivalent to +4 charisma, and immediately gives the impression to others who see him or sense him psychically of Alexian royalty (psychics will explicitly see the Alexian royal seal) and a sense of great power. This explicitly works for psychic switches associated with the Alexian royalty, as the switch will read the character as Alexian royalty.
Warmasks of the Ithin-Kor
|mechskull by noistromo|
Associated Communion: Dark Communion (The Rebellious Beast)
Statistics: Instill Terror 4 , Penetrating Voice 
The fearsome masks worn by an ancient order of assassins and Id-cultists. The mask has the power to focus intense psionic fear on its target, and to expand the voice of the cultist to a terrifying shriek. Otherwise, treat as an light infantry helmet (UT 176).
Associated Communion: Broken Communion (The Other)
Statistics: Castling 
|artifact design by xjager|
The weird, alien planet of Qo was originally a rogue planet, a cold planet that had been shot out of its solar system, even it galaxy, aeons ago by gravitic interactions. Centuries ago, a solar system in this galaxy caught it, and its surface has slowly warmed to hapitability. Among other oddities of the planet, including pockets of twisted psionic energy, are strange stone formations called "Qo stones" by those who visit the planet and steal the relics for themselves. Qo stones allow the carrier to swap places with another ally, provided they are not too far apart, both are willing, and nothing intervenes.
Associated Communion: Broken Communion (Death)
Statistics: "Zombie Ship spell" from Spaceships 7 page 24, 16 character points per ton.
|ghost ship by 5ofnovember|
Sometimes, famous "ghost" ships of legend become infected with Broken Communion. This happens often enough that psions are leery of entering drifting space ruins, for fear of pockets of twisted psionic energy within, but some ships become even more deeply infected with broken psionic energy until then become almost alive with it. They'll seek to trap those that enter, hide from those trying to find their lost crewmen, and then either devour its new passengers or subsume them into its half-living structure as a strange mixture of flesh, machine and the animating force of psychokinetic energy.
Places of Power
Just as items can be infused with the power of communion through the perception of importance, so too can places be infused with power. That is, if a martyr dies at a particular place and it becomes a rallying point for revolution, then it'll will become seeped in the power of the Rebellious Beast. On the other hand, an ancient temple built over a spring reputed to be the birthplace of the local Life Goddess might have a reputation for healing those who swim in its waters.
The easiest way to handle these places is to give them Sanctity levels. A character can create places of power using the appropriate Communion miracles. Consider also offering a minor bonus (between +1 to +2) to certain psi skills at a place with High Sanctity (For example, the rallying point might grant +1 to all Psychokinetic skills used in the area, while the healing pool would grant +2 to Psychic Healing skills). In places of Very High Sanctity, consider increasing the bonus to +3 to +5 or creating a unique psionic effect or communion miracle in the area (the rally point is always affected by a storm, or curses those associated with those who oppress, while the pool actually does heal people). Note that for Broken Communion, whatever effect you offer is still affected by the Twisted psionic energy, but a bonus could off-set the penalty applied.
Of course, none of that is strictly necessary (Sanctity level is enough to know), but it can add a bit of spice to an interesting location.
The same rules that apply to identifying relics applies to identifying (or finding) places of power, though use Connoisseur (Places of Power) instead of Connoisseur (Relics) and allow Architecture to act as a complementary roll.