Jeff,

Actually, it is a very cool idea....You could develop a pretty simple adjustable regulator board, w/ a PIC on it, and provide an interface for setting the discharge rate, curve, time, etc within the firmware running on the PIC.   The firmware could lower the voltage based on the curve, until it's at an unusable voltage. :)

I'll run it by Ringo, and see what he says.  Similar boards may already exist?