Roland TR909 for iPhone and iPod Touch, yesss!!
Here’s another addition to iPhone / iPod touch, the author of the beautiful, minimal iPhoneSynth has created a drum machine inspired by Roland’s classic TR-909. Basic features, but it could be fun to hash out a drum pattern for your next tune on the subway: IR-909 is a drum machine for the iPhone inspired by the Roland TR-909. IR-909 features a 16-step sequencer, 4 patterns, 8 different drum sounds and the ability to adjust tempo(BPM) and shuffle amount.
iPhone Applications at roventskij.net