Developed using Adobe Flash, artists can chooses colors, caps, and stencils for their piece and spray away on your digital canvas.  No respirator and more importantly, no cops.  The demonstration video uses the Wii platform, but since it was developed in Flash, it can probably be adapted for any similar physical interface system.

Unfortunately, to get the full effect, you’ll either need a gigantic screen or a projector.  Although, if you have some friends working in IT on a college campus, you can probably snag a lecture hall with a gigantic projector and just spray away.  There’s no commercial release of Wii Spray just yet, but I bet they would make a killing once it’s monetized.

Source: Wii Spray