Doodle Buddy Premium from Pinger, Inc is an app that does what the name says, it lets you doodle on your iOS device.
I grabbed this app for something to play around with on a sleepy Sunday afternoon. The price point is fantastic being that it is free. There is an optional in-app purchase of $.99 to remove advertisements but I opted to stick with the free version since the ads are not obnoxious in my opinion.