I like cool drawing apps and I found this one online and wonder if there is something like this on the app store. Link to the game http://www.kongregate.com/games/sniegas/symmepaint
its like etch a sketch with a mirror lol. I'm sure it wouldn't be too hard for any dev to make this game for the iphone.
This app is pretty much similar to what you described except that it uses flames instead of a simple lines. Take a look at pic 5 to see both mirrors activated.. ================= App info is currently processing and/or the app is not yet fully available for sale on the US App Store.