I've been working on a USA ePay payment module for the past few days. Things seem to be working fine (strictly in test mode for the time being), and I have been given permission to contribute my work back to the community. I translated most of the "power" (if you can call it that) from the PHP module that is available on USAePay.com. I'm sure if others were to look at the code you'd see ways to make it considerably better.
Again, I should stress that we have not yet used this module for live transactions. If we encounter any problems with it as soon as we go live, I'll be sure to contribute back the necessary patches.
Reported by wheaties.box