Beat Dialer is a 16 step (1 bar) sequencer / drum machine with 20 built-in samples.
There is also a free "Lite" version with only 5 samples.
Known supported devices:
 * HTC Desire
 * Samsung Vibrant
 * HTC Wildfire
Beat Dialer should work on all 240x320, 480x800 and 480x854 devices running Android 2.1 or greater. Beat Dialer requires device support for 44100Hz PCM WAV (mono) - be sure to try the "Lite" version if you're worried.
Instructions:
 * Select samples from the list on the left
 * Use the right dial to to select steps, pressing the centre button to turn the selected sample on or off at the selected step.
 * Press the "Apply to loop" button to apply the new pattern to the audio loop.
 * The headphones icon indicates un-applied changes for that sample's pattern, the speaker icon indicates that the sample is triggered at some point in the current audio loop.