Most people don't know this, but the pitch of a note corresponds to its frequency. Planet Waves prepares to introduce their Headstock Tuner at Winter NAMM 2009, and apparently, the designers were aware of that fact.

You just clip the Headstock Tuner onto your guitar's headstock or bridge and it uses the vibration of the instrument to measure tuning rather than electronic signals or built-in microphones. That means your tuning isn't subject to outside interference, and I can't imagine why it would be subject to inside interference unless one of your bandmates is trying to sabotage you.

The Headstock Tuner provides a multicolor backlit display that teams up with digital needle graphics so you always know what tune it is. When your note is in tune, watch for the red to change to green. The tuning software uses an ultra-sensitive piezo sensor system, which provides increased vibration sensitivity and spot-on note registration.

Senior Product Manager, Brian Vance, talks about the tiny tuner.

“The new Headstock Tuner rounds out Planet Waves’ tuning tool options for musicians. It conveniently clips to virtually any instrument headstock and is self-contained for tuning wherever, whenever. The backlit display also allows for quick and easy tuning on a dark stage, so you’ll never have an excuse to be out of tune again!”