Anyone who does most of their work on a laptop knows the pain of not having a mouse. Since your smartphone is always nearby, it only makes sense to turn it into a mouse. Remote Mouse will let you do just that, but there are definitely some hiccups. It's better than any other free mouse app you can find, though.
Though it calls itself a mouse app, the app is really more of a trackpad. Moving your smartphone like you would a mouse does nothing. In order to set it up, you need to download a desktop app. Sadly, the desktop app occasionally crashes and often hogs your RAM. When Remote Mouse does work, it works incredibly well, though. There is no lag between your movements along the trackpad and the movement of the on-screen cursor. You also have access to a ton of control over what taps and "clicks" do, just like you would with a wired or wireless mouse. The only thing that's missing is triple-click options and keyboard shortcuts. The middle button doesn't behave like it would with a real mouse, either.
Unless you have a giant smartphone or a tiny trackpad on your laptop, you might not enjoy this app much. Remote Mouse has a neat layout and performs well, but it doesn't give you the experience you're probably aiming for. Since it's a free app, it's hard to complain too much, though. You won't find more features in any other free mouse app. If you're looking for more, expect to pay.