If you play guitar or another stringed instrument, you probably have a guitar tuner of some sort. There are a few different tuners around my house, but most of them are pretty large. They’re certainly too big to keep in your pocket, for example. The Seiko Chromatic Tuner Keychain is small enough to use as a keychain fob, so you can always have it with you – even sitting around a campfire with your travel guitar. It has a range of A0 to C8, and it indicates “note deviation in 1 cent increments”. It has a built-in microphone to listen to the note, and to save battery, it will automatically power off after two minutes of not hearing a note. The Seiko Chromatic Tuner Keychain is available for $16.50 at Peripole in the US and for $14.99 at L.A. Music in Canada.