We do just that. We have torque sensor in our trainer. While reasonably accurate it's purpose is not to be an ergometer but provide instant and proper dynamic reaction to your pedaling efforts. However if you have ANT+ power meter on your bike it will uses this power meter to continuously calibrate internal torque sensor during the ride.

You probably will not like the price though ;)

Biggest issue is that ant+ has a data rate of 1Hz for power data, so controlling the trainer based on getting data every second would probably not work well.

I do not see how it could possibly be simpler and cheaper than measuring the speed and estimating the power from that. First, because you you have the cost of power meter, that is much more expensive than a speed sensor. Second, you would need a system that is constantly controlling the resistance, once again more complicated that a normal trainer that varies resistance based only on speed.

Isn't the limit from BT significantly higher? I wouldn't be surprised if most power meters move that way in the next couple years anyway...

Looks awesome, I have been looking for exactly something like that which uses just a roller and bodyweight for the back (like my elite fluid trainer) and a clamp for the front fork mount. Looks quite portable as well which is huge for me. When I win the lottery you guys will be one of the first places I call!

I think he's talking about about a power meter on the bike e.g. crank/hub/pedal based that a person might use while they're also on the road. Just off the top of my head, if you had something like a Kurt Kinetic Road Machine, you might be able to achieve this with a servo connected to the screw that controls how tightly the trainer is clamped to the tire (PATENT PENDING... pink?). There would probably be a limited power range in which this approach would work (e.g. I doubt you could go from 150w to 400w at the same wheel speed).

... could be a fun arduino project for the winter.

http://forum.slowtwitch.com/gforum.cgi?post=5396505