Wave is a free Android application which is a chromatic tuner.
I feel it is neatly done and it is very stable.
It is capable of playing the reference note, if you want to tune with the ear.
I have compared it to all my other tuners, it appears to be extreamly precise, and well selective on the first hormonic, which is not so frequent.
As it is the one I always have in my pocket, it is eventually the one I use the most.
It replaces the already very good “gString”. It is freely available on Google Play.