Endgame practice

It would seem to me the best way to practice endgames would be to have some sort of software that allows you to play multiple variations on the same theme. For example, R+P vs R, but with the pieces starting in different locations every time you attempt the problem. chess.com's position trainer is good but the starting position is the same every time, and depending on the endgame the approach/result can be very different depending on the starting position. 

It seems a lot of people are manually setting up various positions and playing them against the computer...but the approach above seems like it would be so much more efficient. Yet I haven't come across anything like that yet. Does anyone have any recommendations?

There is an endgame trainer in the Apple app store I just got, you could try that out.