Sketching is not so hard. It is really interesting to sketch something with basic tools. Here is an attempt to sketch a Mind Mapping tool for iPad. It is real fun to sketch for a touch device. In fact, that was our first experience with paper animation and video techniques, but I think the end result is good enough for 6 hours of work (taking into consideration that we've learned iMovie on the go).
The application is pretty simple. You can create nodes and connect them, delete and move nodes — all with simple gestures.
The video goes at 2x speed. It is more dynamic this way, but maybe some details are lost...?