(Oops posted in the wrong place initially)
It's no replacement for Lascaux or these oekaki apps, but it's really cool to play with and get some nice abstract artwork out of it.
Go play! It makes nice looking images even using a touch pad :P
http://mrdoob.com/projects/harmony/

Yea..harmony is fun ..

Indeed it is fun :D.

I like it, thanks! :)

And it works on the iPad. :D