Sauron, Call Your Service

One Ring to rule them, and one Ring to find them, One Ring to bring them, and in the dark bind them.

It isn't quite like that, but the Remember Ring is a first step. Slip this on your finger and it's programmed to heat up to 120 degrees Fahrenheit on a specific day *cough* anniversary *cough* every hour for 24 hours-- and it runs on a thermopile that makes electricity from your body heat, so you can't hope for the batteries to run down.

My wife is fitting me up for one as we speak.