I'm working on an app called ScreenHint. It lets you take a screenshot of a bit of your screen, which then floats there above your other windows until you dismiss it. It's essentially a clone of the sadly-abandoned Snappy, if you're familiar with it. There are a lot of things I wish it could do still, but I'm worried that I'm missing some ease-of-use and polish items still. The app is free and is currently on the mac app store, but I haven't really done much to promote it yet.

https://www.screenhint.com/