We actually do support Android. Any device that supports Bluetooth 4.0 and Bluetooth Midi can be used with Freedrum.
Unfortunately Android has an audio latency problem. In non-technical terms, it won't play the drum sound immediately when you hit, instead it will be a few milliseconds too late.
In technical terms, look here: http://www.androidpolice.com/2015/11/13/android-audio-latency-in-depth-its-getting-better-especially-with-the-nexus-5x-and-6p/
Android is getting better and better at this with each version, so we do not doubt that they will support Freedrum in the near future.