I think most electronic rangefinders nowadays do the same thing. Leupold calls it TBR, True Ballistics Range. They have preprogrammed some popular balistics into the range finder, you select the mode that fits your gun and it automatically calculates and reads the slope adjusted range. I've found mine to be fairly accurate for rifle and bow, but hear that Swaro rangefinders have it nailed down a little better.
It would be a good back-up if your rangefinder does not have that capability.
thanks guys. being a transplated flatlander, i don't get much opportunity to practice incline/decline shots very often. might look into an angle comp rangefinder.