The Wii Spray concept project by University of Weimar's Martin Lihs is now a reality, as you can see in this video. You can pick colors pointing at patches, and even use stencils.
The toy itself doesn't require a Wii to work: It uses Flash on a normal PC as the platform, and the Wiimote as the controller. However, I wish Nintendo and its developers could look at this and be more creative about the use of the Wiimote. Even while this will require a big screen, I think kids will love to paint like this on their TVs, while parents will be happy for them not use spray or crayons over real walls. [CLDFX]