(Free) This remote access app is probably one of the most powerful free apps out there. With TeamViewer, you can manage your desktop computer or another smartphone right from your iPhone. All you have to do is install TeamViewer on both your computer and iPhone and you'll be able to control your computer remotely—simply by entering in a master password! You can transfer files between devices and even print documents, no problem. This is a great tool to expand your phone capabilities when working on the go, and is also a great way to help a coworker or friend who's experiencing technical difficulties.