It doesn't evaporate so much as it sort of sinks. You shouldn't feel bad about not being entirely clear on how it works, though - Skuld isn't entirely clear on how it works, and she made it. :)

I had a whole range of abilities sketched out that were going to follow on that bit of Twilight, but most of them ended up being too cumbersome to integrate properly with the Story at Large and were quietly shelved. About the only one that's left is that the arm computer can conceal itself when surplus to requirements (which it is most of the time, these days, because the omni-tool's holographic interface does most of what it does, only better).

Part of the problem with omni-tools is that, because the user interface of the device is apparently independent of the device itself, it's never clear in the game what the machine itself actually is. It doesn't appear to be a wrist-mounted device, since characters often use them when wearing those short-sleeved duty uniforms. It might actually be an implant of some description (as the in-game encyclopedia noted that the haptic holocontrol interface things are), though again, it's never specified where or how big it is, or how much of a production is is to get one installed.

As such, I've always had to be a bit vague about just what and where they are, for the characters who have them. Quarians can presumably integrate them with their biosuits, but all we know for sure about Jen Rossum's, for instance, is that you'd need a saw to remove it, which implies that it's a limb implant of some sort. In G's case, it most likely is integrated with his bionic arm computer thingy, simply because that'd be the most efficient way of handling it.

Whatever the case, he's at pains to keep it on the downlow in 1946, because the disruptive potential of the technologies it embodies are on a much higher order of magnitude than, say, the mostly-invisible passive neural switching technology in Mio's goggles. And because picking up a wrench when Ursula or Shirley is slinging one next to him is neighborly. And because I sometimes forget he has it. :)

--G.
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Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
zgryphon at that email service Google has
Ceterum censeo Carthaginem esse delendam.