This is something that makes Linux much smarter than Windows. With little bit of work you will be ready to mock at Windows Media Center PCs. There are many remote software for Windows platform, but all combined together can not beat this open-source project named – anyRemote!
It works with Nokia, SonyEricsson, Motorola, Samsung and with virtually every Java enabled cell phone which can connect to PC using any medium (Bluetooth, InfraRed, Cable, Wi-Fi, GPRS)
You can use it via command-line as well as GUI. Moreover separate KDE and GNOME frontend available with bonus web interface!
Not to mention, you can be configure it to use with any application on PC.
I have tested this on my Fedore Core 7 64-bit PC with Nokia N-70 cell phone. I used KDE interface. What I loved most and missed in every other application like this is ability to browse entire file-system from cell phone. This helps me changing songs, videos without ever going to my PC!
This is open-source and completely free project with many packages available for download. You atleast needs two package, one for PC & one for mobile!
Also note one common mistake I still keep on repeating while using this software. I forget to turn on Bluetooth before starting mobile client. Being written in JAVA, client on your handset, starting can not turn your Bluetooth automatically. You have to turn it on explicitly.