My fitness coach, it's kinda of like a workout video though, but it'll get your heart pumping and it can be customised to your time frame and what your trying to do, (lose weight, increase flexibility, stamina, etc. )
There are several out there, Wii Fit Plus is great because it has so many different games / activities you can play and they are a lot of fun. Most of them require the balance board though. EA Sports Active is a good one and it does not require the balance board, but you do have to have the nun-chucks. I have been wanting to try the Walk It Out program but it requires a DDR mat, so I have not gotten that one yet.