Garage band uses the accelerometer to do velocity-sensitive drumpads (article here about the fabulous technology used to achieve this). While we applaud this fantasic use of the accelerometer, we have gone another way with drumpads: position sensitivity.
Position-sensitivity is an amazing thing, and when you try it (with the MIDI target of your choice, though we did a lot of testing with MoDrum on iPad) we think you'll agree.
How to set it up: the article on position-sensitive Drumpads in MIDI Designer is here.