You have to account for the cost of the equipment to capture and store or convert the energy for use elsewhere, which for the energy of a squirrel, would not be very dense. Not to mention you'd have to get it past the animal rights people.

How much energy do you think a squirrel can generate? I doubt it would be worth the trouble.

Squirrels rights!

I appreciate the comments. :D Squirrel rights indeed! I don't propose caging them, though. Just letting them do their thing naturally... and the point beyond that is that there's a lot of energy potential in the movement that happens throughout our environments all the time. We should be able to exploit the movement without being exploitative.

That's a very creative idea, but any plan using animals (including humans) for energy production is probably not going to have much merit because of the inefficiencies in animal metabolism.