I doodled this on my sketch book at work, snap a photo of it and painted it on my cell phone lol! The app is called Picsart--Photo Studio and it's a very powerful art program, or at least powerful for a cell phone app ...but, I think this app needs a layer feature and dodge and burn tools lol! Otherwise, I highly recommend this app if you're always away from your computer, if you're too tired/lazy to luggage your laptop outdoors, or both
Though, I think Picsart is only available for Android users. I don't know any equivalents for the iPhone or Blackberry :/