Cute little cars? Check. Pencils? Check. Now you're ready for the Basement 500. Lineriders follow dark lines you've drawn on any flat surface and you can even race them against each other.
No special surface is needed and they'll follow annotations to speed up and slow down. Do they exist? Probably not, but the concept is killer.
Lineriders, Hotwheels Revisited [OhGizmo]