Electronic tuners are nothing new, they've been around for quite some time now and while most of them are very portable they do require carrying around another piece of hardware, until now thanks to Chromatic Tuner a freeware Symbian application that's very easy to master.
How It Works:
Chromatic Tuner uses your Symbian S60 devices microphone to pull in musical notes as you play them and then via a technology known as FFT your device determines the frequency at which those notes are played.
To test the application I played several notes using a guitar and once tuned via my Nokia Smartphone I then played those same noted via my Behringer Tuner, after testing I must admit the phone enabled notes were extremely accurate, I had my doubts at first, however considering the Symbian tuner actually recordered frequencies down to the 10th of a Hz I probably shouldn't have been so surprised.
I particularly liked that the tuner used a sliding sliding scale that displayed the Hz as they increased or decreased, this was much like what you would find on a standard tuner as it went between flats, sharps and base notes, except since the frequency is more finely tuned you can gain a better perspective on how close you are to achieving the note you're tuning your instrument towards.
To see what the Frequency and notes information looks like I've included the following screenshot: (Click To Enlarge):