Metronome free (vd63.utilitaires.metronome_gratuit) on Google Play
This application allows you to turn your phone or your tablet into a metronome which can give a pace from 5 bpm to 300 bpm, with the possibility to add a cycle (different sound every n beeps). It is also possible to emit an la 440Hz to help you tune your instruments.This application is also available in paid version, without ads.