Definately talk to a physio as suggested. I did use the Wii Fit – the yoga balancing was really good – but NOT to begin with. I tried it and it was far too painful until I'd got some control and strength back…but balancing is just as good.
I imagine a wobble board would be even more painful to begin with, but I suppose it's dependant on the amount of damage you've done. The Physio gave me some good "lunge" type excercises where you rotate (obviously a small amount initially. That helped get some movement back quite quickly.
I began to feel like a bear in a zoo as I was constantly doing those heel lifts. The other thing to bear in mind is don't overdo it. I had a couple of very painful days where I'd gone overboard with the excercises and my ankle just swelled back up like a melon.
Overall though I found the bike a really good form of excercise, particularly low load / high cadence., but you do need more orbit type excercises as well as the pedal stroke is pretty limited in its range.
When you do go outside you'll be suprised how painful stopping and putting your foot down can be early on. In this weather I wouldn't risk it until you have some strength back.