iOS developer Beep Street - who also make the very well respected Sunrizer Synth, haveposted a teaser for their just submitted drum synth App IMPAKTOR. Looks like it uses the iPhones built-n sensors to interpret vibrations of you hitting the sirface it is sitting on to trigger the on-board sounds. Also appears to be a 6 track loop recorder to build up rhythms as you go.
For iPhone, iPod Touch (4th Gen) and iPads - available soon.
4-voice paraphonic synth,2 osc, 3 filters,5 LFO, 5 ENV + 12 slot matrix