The Ukulele tuner app is a great tuner. Apart from it showing and playing the notes of each string it has a list of chords you can learn to play. It however cannot detect the chords you are playing. Loud noises will make it unable to detect the notes you are playing. The tuning can be changed as well as the reference pitch and the note names. The Ukulele tuner is a small app available for Android. It has a Premium version as well on Google Play. Both versions require Android 2.3 or newer.