Here is a shot of my laptop with my modifed nook color running touchDaw.
this was one of the reasons I wanted a tablet in the first place. so far the latency is pretty low. Touch has a mixer, keyboard, and XY pad controlers.
Check out it there is a free version that will let you see if it will work for you. You do have to go to the website to get the setup instructions for the wifi midi set up.
