Need Software to Measure Dimensions in JPG

I need a program that will allow me to determine dimensions of pictures I take with my digital camera.

For example, if it take a picture of a house and tell the program that from "Point A" to "Point B" is 36 feet, then the program can determine the proper scale of the picture. Since the program now knows the dimensions of two points, I should be able to find other dimensions/distances of other points on the same picture.

I vaguely remember seeing something like this in the past but now I can't find it.

Please let me know of any software that will do something like this. Thanks!