Well, I wasn't going to post it, but I made one that went in 4 dimensions; X, Y, Z, and through time! There!
Seriously, to get more current capability out of a regular servo driver board, you'd just have to beef up the H-bridge drive circuit. That, coupled with a larger motor, could be used as a steering servo for larger vehicles without needing to get a huge/multiple (and expensive) servo. One of the servos that would be good for this would be the ones that can use 2s lipo directly.
One thing I had noticed though was that the speed was variable, but not nearly as proportional as a real ESC. Good for a servo, but not so good as a truly proportional control.