Thanks, all excellent advice. I have been tempted to try out those remote controlled collars at the store, but wanted to exhaust all the 'simple' options before going there... (I think this is a pretty cool tool though).
I love the wheel imagery. That's what I'm going for; I always want to occupy even a tiny portion of her brain, so at least I'll register... and it will be FUN for her to speed back.
She does this very well (stays within my "wheel") on the 'extendi-leash' (one of those 15m ones that automatically rolls up). She even loves racing back to me to continue on our walk or jog, when I tell her to 'come on!'. I guess it will just take more training for completely off-leash - so I should stick to it! I've already bought a really long piece of rope so I will start giving it a try!