Audioid

Audioid is an advanced mobile electronic music rhythm composer for Android, combining drum machines similar to the mythical TR-808 and TR-909, two legendary TB-303-like basslines acting as grooveboxes and an interesting Metropolis (M-185-like) sequencer linked to a virtual analog synthesizer engine with dual oscillators, ADSR envelopes, 4x LFOs, basic FM, phase offset modulation; all coupled with real-time filters, effects, randomness and a live approach.

Audioid is also a nice proof-of-concept showing that DSP and real-time audio synthesis can benefit of parallel computations (provided by RenderScript on Android).

You can get Audioid on Google Play, there is a free and a paid version available. The free version has only few limitations compared to the full version, it displays ads, you cannot open your saved projects, you are restricted to 2 FX entries and 2 LFO entries (instead of 4) per machine and only bipolar LFO waveforms are allowed.