The idea isn't novel. A student submits a homework pass instead of a homework assignment and still receives credit. It's a practical reward that students will have a felt-need to work toward earning for themselves.
This is a sheet of ten color homework passes. Each pass is 2 inches high and 3.5 inches wide. Simply print out a sheet of passes and cut them out. Write the students name on the line.
Give as a reward for exceptional work
Prizes for classroom games
Consider letting students save passes to trade in for a larger prize