There are a few folks who have built homemade electronic instruments, but not many. A large part of the homebuilt world is old school, people want steam gauges in a biplane, for example. The go-fast crowd wants proven reliable instruments for IFR flying. And the rest, once they've built their plane just want to put some instruments and fly, instead of continuing to tinker.

But there are a few I've seen, especially in the sailplane world, which is modern but strictly VFR. And I think there was some discussion about Arduino based instruments over on the homebuiltairplanes.com forum.