Eason, any chance of some more details on how it works?
Direct from Eason, here is more detail
I am rebuilding it and trying to post everything about it on my blog. There are three posts about it:
Demo code without Android, which draws a square: http://blog.easonke.com/nxt_painter_demo_code/
Some math behind demo code: http://blog.easonke.com/nxt_painter_code_model/
I will continue to post android part. Lejos is used. The android application collects touch events like up/down/moveTo(10,10) and sends them to NXT thru BT. NXT just follows all events.