btrd, get a balance/wobble board.
One of things with a ball on the bottom, OR you could make a simple one like this pretty easily I reckon, jump on it when watching the idiot box.
I've been mucking around on one at my brothers place, only intermittently, but I have noticed a HUGE difference in achilles pain aswell as foot discomfort. Admitedly the achilles pain stems from skateboarding, but the foot pain whilst SUP'ing is pretty much non existent now aswell.