The Spin the Wheel  app allows you to set up an entry form that users need to fill in and then they get the chance of trying their luck by spinning the wheel to see if they've won one of the prizes you've set up in the promotion.

This wheel is spun to choose a contestant at random, who is lifted up in their chair to the main stage. In each round, the contestant chooses a subject, the seat of whose expert lights up gold, and also an expert to "shut down"  the one they believe is least likely to know about it, whose seat lights up red.