Mobile Metronome: Free!
Mobile Metronome is the best rated free metronome on the Android Market. It is easy to use, robust and has everything any musician can ask from a metronome. List of features: Fine tempo tuning from 10 to 230 BPM; tap tempo; adjustable tempo; signature for simple, compound and complex meters; from 2 to 20 beats per measure; beat subdivision as quarter, eighth, triplet, sixteenth, quintuplet and sextuplet notes.
gStrings is a chromatic tuner application measuring sound pitch and intensity. It will let you tune any musical instrument such as the violin, viola, cello, bass, guitar, piano, or wind instruments.