|Pretty good for an old building!|
iPinPoint is an iPhone app that will work on your iPad as well. This is how it works. Take a picture with your iPad camera or from inside the app. Then choose which function you would like to use: angle or distance. If you choose "angle", then place three points on the picture to determine the angle. If you choose "distance", you mark a known distance on your picture first, then choose another distance to measure. I find this function to be a bit more difficult to manage, so it will take some practice for students to use well.
I came across iPinPoint after a junior high math teacher invited me over to observe. The students marched out into the school armed only with iPhones or iPads and a clipboard for data collection. Their task was to find specific angles around the school in a scavenger hunt. Once they thought they found one, they would take a picture and record the angle.
Like a lot of apps, iPinPoint teases you with its features and then wants more. Unfortunately, you have to upgrade to the pro version to save your marked images. The pro version also allows you to measure circles and triangles. I would argue that $.99 is a good price for those extra features.
I hope you find iPinPoint useful! Let me know if you've used it or know of any other apps that are better!