At Halfbakery , you'll find ideas that have been thought up, but not necessarily thought through. Not that that's a bad thing. Well, it could happen. Give kids a self-powered radio frequency ID device to tie on their shoes when they enter an amusement park. Bury transponder loops all over the park and in turnstyles, food stands, shops, interactive info kiosks, etc.
Boxes contain a sandwich, fries, a drink and a 'toy'.
A digital counter that goes on the roof of your car, and comes with a remote control that has two buttons. If somebody lets you into the lane, give them a good Car-ma point. If somebody cuts you off without signalling, give them a bad Car-ma point. If you need a creative spark, you'll find plenty of possibilities. At best, you'll find inspiration.