You can buy geek glasses but not, as far as I'm aware geek detector glasses; so that when I "take" them to class they are, like some of the things in Tim O'Brien's short story, one of the things I carry in my head, rather than on it.
What I mean is this: right from the start of the year, on the first day, go into class and find out which of your kids are good, really good with technology, and enlist their help for the rest of the year.
You don't need "geek detector glasses"; and you don't in fact want to use the word "geek" at all.
Apart from wearing unflattering glasses, geeks tend (and I speak from experience 🙂 ) to be social outcasts, especially if we're talking teenagers, and you don't want to poke any more fun than is perhaps already being poked at them.
It's actually a fairly safe bet that lots of your young learners are fairly good with technology. They're also often fairly lazy and will turn to you for help when they get stuck with technology.
As a general rule, I "never" help learners with the classroom technology they are using. Instead, get them into the good habit of turning (1) to a partner; failing that (2) to the pair sitting next to them; failing that (3) to your "geek".
Rather than call your geek by that pejorative term, call him (or her) "technical support", and remember to thank him/her afterwards.
If you're lucky, you have several "geeks" in your class; get the rest into the habit of turning to (1) or (2), above, if they need help; and if that doesn't fix the problem, to put their hand up and call out "technical support". Your assistant/s — not you — should then get up and go help fairly immediately.
If you're really lucky, your school has something (4) like this brilliant scheme for the kids providing the service systematically.
Identify that geeky kid, get him/her to help you and it will take away so much of the teacher's fear of using classroom technology; and by appreciating and valuing that kid you may be helping him/her, too…