The Glucoboy is a blood glucose meter built into Game Boy Advance cartridge. The more a child tests his blood sugar, the more points he earns, unlocking mini-games.
Perhaps it will be incentive enough if it's the only cartridge they own, but obviously nothing is stopping the kids from popping in another game instead of sticking themselves with a pin. Still, can't hurt, right?
The Glucoboy is available down under for $260 down under dollars.