Okay I'm not going to lie. This works pretty well. I've had it for about 9 months now, until it stopped reading my heart. It now says that I have 200+ bpm constantly, no matter what I do or it would give me an error. During that time when it did work, it was pretty reliable except for sometimes when it would give you sporadic excessively high beats. It doesn't link up to your computer on its own. You'll have to buy a link to do that.
However if you are serious about training and want to spend some money, you can track your progress online from calories, time, and even miles if you buy the footpod or gps sensor. It tracks progress the watch, but online is nicer. I didn't buy any accessories to track the miles I ran because things were getting a little expensive.
Hope fully the photo helps, so people can get an idea of its size.
The battery lasts for about a year.