If you use a metronome, then check out Planet Waves new model with a tuner in it as well
The Universal Chromatic Tuner is described as ‘a working musician’s tuner with a twist’. Obviously it’s not exclusive to working musicians, so jazzers needn’t worry (ker-tish!). The ‘twist’ is a fold-out bracket that hangs from the soundhole of an acoustic guitar for ‘hands free tuning’. Don’t worry, we checked with the distributor and you can still use your hands – it’s just that you don’t have to use them to hold the tuner. This latter feature works fine, although you can’t actually see the LCD or LED displays… but never mind, you can prop it up picture frame style on any surface.
The Metronome Tuner has dual mode operation for auto or manual tuning via an integral condenser microphone. It can be calibrated to any pitch from A410 to A470, it’s accurate to +/- 3 cents, and the tuner employs an LCD-style needle display and a green ‘you’re there’ LED.
The other ‘twist’ is an impressively sophisticated metronome mode with volume adjustment and both visual and audible references: the first beat has a higher pitch, and the display flashes red. The tempo can be set anywhere in a range from 20 to 250bpm and you can easily adjust the number of beats per measure to practice various time signatures such as 2/4, 3/4, 4/4, and so on. The Sub Menu allows you to subdivide the beat in 1/4 notes, 1/8 notes, triplets and so forth. There’s even a pitchpipe tuning reference from C2 to C6, a jack socket for input and a mini-jack for headphones.
This simple-to-use device is packed with features and because it uses one of those round, flat watch batteries, it's small enough to slip into your pocket. You certainly get your +/- 3 cents worth.