GlanceCam is an app developed by my friend, Cesare Forelli, and it's once that I've admired for a long time. In short, it's an app that lets you view IP cameras from your Mac. But in reality it's so much more, especially with the recent major update.
It's a relatively minimal design, however it's still packed full of functionality. It support multi-windows, always on top, 4K streams, you can use it to sent HTTP GET commands to your devices, keyboard shortcuts, a URL scheme, AppleScript support, and so much more.
This app is probably the main reason why I'm thinking of investing in some cameras for my house.