The problem with this is that there wouldn't be much usable output. I think a person has to peddle fairly hard just to keep a 60 watt bulb glowing--or that's my recollection. A TV would be way too much.

Actually, sport cyclists can generate 350 watts for fairly continuous periods (an hour)and the racers can surpass 400. But I suppose you're average overweight-home exerciser wouldn't be able to do quite that much. Still, 100 watts could supply a faily good sized flat screen, something like the size of a laptop computer.

If you check google, you find that this idea is pretty well known. From reading various sites, it appears that a typical healthy human can only generate about 100 watts continuously. A world class cyclist can do better, but not that much, about 200 watts.

This is pretty much already available and currently in use at The Green MicroGym in Portland, Oregon. They have a series of stationary bike generators linked for greater power output. I believe there are commercially available models, but they don't produce a ton of energy- enough to recharge your phone or laptop though!