I’ve mentioned before a program I’ve made called AlDraw. It’s used for making geometrical designs. Here are some examples of what I’ve done with it. I’ve also made a wiki about it.
Well, now I’ve made an Android app version of it.
So if you have a device that uses Android 3.0 or higher, give it a try. Tell me what you think.
I’d appreciate any feedback.
I just tried it on my Nexus 7 – pretty neat! I think the color selector could maybe use one of those 2D gradient palette things. Also, could maybe use a shortcut to place mark points at integral subdivisions of an arc; I was trying to divide the initial circle into five, and having a merry time of it. 
Also also, it seems to crash if you zoom really far out (around six full-screen pinches) while there are any infinite lines in the shape.