Using the iPhone's microphone, the NHL's new Hardest Shot app can actually measure the speed of your slapshot and your NHL potential. With the right setup of course.
First you'll need the hockey basics, like a rink, equipment, and a frozen puck, as well as $2 for the app itself. You'll need to aim at a solid surface, not a net, because the app listens for the sound of the actual shot followed by it hitting the target. So once you specify the distance (anywhere from 20 to 40 feet) it calculates the speed of your shot based on the time delay.