I just bought Air Display by Avatron, a secondary display app for $9.99.
Seems to work pretty well with stuff like Spotify or iTunes... it seems to be a piece of crap with HC chat/web pages in general (iPad 1, maybe iPad 2/3/HD/etc will work better.)
You can enable touch on it which seems to work pretty well. The app works over wifi, and it seems now you can do an ad-hoc connection if need be.
I had a hangup with screen rotation (Windows + iPad, though you can do quite a few different combinations between desktop and mobile platforms), but with a little messing around with it, and trying to lock the screen rotation, it seems to work rather well.
I have some remote desktop apps, but maybe I'll use this one a little more.
**BRENT**