Ultimate Mouse Lite connects your iPhone to a desktop as a wireless mouse and pointer. The system works decently well, though setup and interface obstacles can make it needlessly complicated to use, especially when compared to some of the other options currently on the App Store.
Ultimate Mouse Lite won't do anything until you install the desktop client and create a "receiver." Receivers must be on, with the software running on the desktop. Your phone will then see any receivers on the same Wi-Fi network and connect when you tap them. This is a slow process, made even slower due to spotty connection issues and a buggy desktop app. It works, but it just takes time to get started. The value of an app like this is not immediately apparent, but with both a pointer and full mouse mode for the app, it can be used as a pointer when giving presentations on a projector, something that provides a much-needed augmentation of your desktop and your phone, alike.
Ultimate Mouse Lite works decently for a free digital mouse replacement. It's not perfect by any means and because of a muddled interface and slow connection speeds with occasional hiccups, there are better options out there; but if you need a free app that will handle connections between iOS and desktop to use your phone as a pointer, this will work well enough in a pinch.