Was looking up ideas to get kitty to exercise more and stumbled upon this. Apparently they manufacture these at: http://www.catwheelcompany.com/
There are multiple youtube videos that make this look pretty successful. Mostly vids of bengal cats but some domestic cats too:
These vids make the wheels look pretty effective at increasing exercise...maybe they are worth a shot? I mean, vids of other toys like panic mouse often have a few bored cats but all the vids for the wheel show some interest.