The story a while back about connecting an iPhone to an iPad for a game of darts was pretty interesting, and here's another one in that vein: a new app called Remote Palette is universal for both devices, and will let you "paint" on the iPad, while controlling the colors used with the iPhone. "Dip" your finger into a certain color of paint on your iPhone, and then when you go to touch the iPad, that color will show up as you draw. Very cool idea, and while the reviews on the app say it's not quite as great an art app as Brushes or Sketches, the wireless palette idea seems like a lot of fun.
Remote Palette also has a Finger Paint mode you can use to put some outlines on the screen for kids, or you can just open up a blank canvas and paint away. The universal app is only US 99 cents, and is available right now.