If you have a Nokia 3650 mobile phone and a Bluetooth-enabled Mac running Mac OS X (10.2 or higher), you can use the phone as a universal remote control, thanks to the US$8
Veta Universal 1.0
Veta Universal is installed on the Nokia 3650 phone itself; it works in conjunction with the freeware Romeo application that is installed on your Mac. The combination allows you to remotely operate such Mac applications as iTunes, the QuickTime Player, DVD Player, and Keynote.
Romeo, available as a free download from Arboreal Software, not only can you control applications, but you can also use your mobile phone as a mouse or as a volume control. Romeo is an open source application. The latest version is 0.9.1, which offers multiple monitor support for the mouse, scrollwheel emulation, and more.