This is the only piano/keyboard app I could find that actually supports Bluetooth keyboards, and it works great!
The only issue is that I cant find any way to press more than one key at a time, but Im pretty sure thats an issue that lies in the way Apple chose to support keyboards and theres nothing the developers can do about it.
So it gets 5 stars anyway, and its still well worth it for messing around and simple melodies!
The_Moose_ about Double Decker