If you love playing guitars,  the StroboPick Guitar Tuner is a pretty cool gadget to have. Shaped like a guitar pick, this amazingly small guitar tuner works with strobing LEDs.

"By shining a flashing light at a vibrating string you can clearly see whether the string is in tune with the light source. StroboPick emits 6 light frequencies matching standard guitar tuning with great precision."

Pretty cool, just like the PowerTune. Here's a video demonstration of the StroboPick. Unfortunately, they are currently all sold out.