ArcNote is an app that's difficult to describe in a few, short words. So, let me have some visuals do the talking. Look at the screenshots below, and you'll probably pretty quickly understand what this app does.
Now that you've looked at them, you probably realize this is kind-of-sort-of amazing. If you're constantly in meetings, or attend some kind of higher education institution, you probably see a lot of PowerPoint / Keynote slides. This app lets you take a picture of a slide presentation while also simultaneously recording audio, and those pictures can then be transformed / tweaked into properly-oriented, full-sized slides.
I tried it with my computer monitor at a fairly awkward angle, and it worked scarily well. I think the video (below) is a little optimistic about the distances you'll be able to achieve usable results at, but even so, this app is unlike anything else I've ever seen, and it solves a real-world problem I definitely had when I was in college. Head to the Play Store link below to give it a shot.