Smart Racket Coach
Design a tennis racket using MEMS technology to give audio feedback for at least the following: Sweet spot accuracy, racket head angle at contact, force of contact. This way, new players, as well as intermediate players could get feedback as if a coach was on the court with them.
Design it into the grip so that existing rackets could be retrofitted. This would be a nicety. And make the 'MEMS Coach' more marketable.
Reward: I would love to have one of these rackets for my wife