are you doing much with your customers in the way of mobile?

Very, very little. I think we've done maybe 2 jobs involving cell phones/tablets in the 4ish years I've worked there (and they were friends of the boss). There is a cell phone repair shop in the next building over, so we usually direct people over there instead. My boss doesn't really want the liability of breaking someone's phone/tablet due to the stupidly thin cables or delicate construction or something.

It does seem like something that would keep you marketable, but you would probably want to do a bit of research on what other companies are charging so you don't over/under charge for your service.