I use an old fork.
I dremel'd out the middle two bits and cut down the remaining two at the thickness that exactly matches the cap.
It has proved quite usefull.
Another tip is to run the end of the pedal under the hot tap for a while and rub a bit of washing up liquid round the edge of the cap.
Warming it up 1st and rubbing something in to lubricate it usually helps the unscrewing go more smoothly.