The Intellitouch Tuner is an electronic tuner for string instruments which I have found to be reliable in almost all conditions. I’ve used mine with guitars, mandolin, and mandola for several years and have had nothing but great success.
Intellitouch Tuners don’t have microphones, like most electronic tuners do, or patch cord inputs (for electric guitars). Instead they clip onto the headstock of just about any stringed instrument and give a readout of the exact pitch of a note by reading the vibrations through the neck of the guitar, bass, violin, mandolin, or whatever. The benefit of these tuners is that they can be used in noisy environments, like bluegrass sessions or stage performances, whereas conventional tuners are completely scrambled by a noisy environment. Since you can leave them clipped onto the headstock for any length of time you like, you can stay in perfect tune without having to step back and use your ears or try to get a good reading from a microphone-driven tuner. They are chromatic, reading all the accidentals and natural notes, and displaying them with three arrows on either side that tell you whether you’re sharp or flat. And best of all, they’re backlit and easy to read.
At the weekly bluegrass session I drop in on now and then, it appears as if everyone has one of these clipped to their instrument. But the result is terrific — even if not all of us can quite keep up with the tempo or remember the words to a song, at least we’re in tune. The company that makes it looks to be introducing a similar tuner for brass and woodwind instruments, perhaps helping high school bands actually sound — uh, better?