It doesn't need the app. You can use their stuff without it. If you want to use some of their more advanced features, you need to use the app. For example, I

It doesn't need the app. You can use their stuff without it. If you want to use some of their more advanced features, you need to use the app. For example, I have it setup so that if my macbook is on, I can push my cursor to the far left of my windows screen and my mouse will automatically switch to the macbook bringing along anything in the clipboard.