An armband that you pay a subscription for. It hooks up to the internet every night and you get information about how many calories you burned, how much you walked, ran, etc. You can input swimming or exercise and food that weren't directly put in. It is good for someone to get started, but $$
It was pricey. It works as well as anything-that is you have to actually DO it, wear it. Spark People does the same thing without the technology and it's free. I used it for about 6 months, didn't lose a lot of weight. Now I am eating healthy and exercising without spending money.