If it's been a while since you raised a good, honest sweat but really have no inclination to venture too far from your PS2, the Gamercize GZ Sport might be the answer.
Connect it to your PS2, stand on the two pedals and use an attached controller to play whatever game you want. Here's the catch - if you stop pumping away on the pedals, the controller stops working!
This is a violation of the bill of rights! Pure cruel and inhumane punishment!
Hmm, that seems fine for PS2 games that have short missions and frequent save points, but what about long ones like Final Fantasy or MGS? And what if nature calls?