A self-tuning guitar?

It'll probably be 10 years before this becomes standard -- if it ever does -- but it could really make guitar playing a lot more fun. I hate tuning, especially when I just want to play a few notes in between other tasks. Also, in college I played in a band that did "You Shook Me All Night Long," and one time my G string slipped a bit flat before we started (for non-players: that's really, really bad).

It could also spark a resurgence of alternate tunings. I've messed around with them at various points in my evolution as a player, but once you've tuned your guitar to (as I once did) Eb G Db G Bb F, you can't play your stock riffs until you put it back into "normal" mode. This would make the process a breeze.

Instruction manual here.