Uh, I think this is actually getting worse confusion-wise!

I believe he meant you could use a hydraulic disc-brake caliper, the cylinder of which you would power with a strong servo or similar instead of with your hand. So imagine the brake handle on a bike powered by a servo, and the flywheel is the bike wheel.

I don't think it would work. It would slip, which would sap up power. It would have the grip at full compression of the caliper to do the job, perhaps, but in getting there it'll slip, causing all sorts of problems. It would have to be a locking pin like system.