Any bluetooth dongle will work. Im using some Planet bluetooth adapter from stone age and its working perfectly. And if you can, try to find adapter that have bluesoleil software included.
Intel Core i7 2600K 2.8Ghz
Nvidia Geforce 570GTX
8GB RAM DDR5
Belkin F8T017 Bluetooth dongle with WIDCOMM stack
OS: Windows XP
Star this issue: http://code.google.com/p/dolphin-emu/issues/detail?id=4833
3rd party wiimotes and nunchunks, original motion plus.
Nvidia Geforce 570GTX
8GB RAM DDR5
Belkin F8T017 Bluetooth dongle with WIDCOMM stack
OS: Windows XP
Star this issue: http://code.google.com/p/dolphin-emu/issues/detail?id=4833
3rd party wiimotes and nunchunks, original motion plus.

. So don't loose your nerves, i'm trying to help out some dudes with my personnal experience of Dolphin. I don't know about coding, but coders need testers and feedback of users to improve their programs. So, i can help...
English is not my native language too so I make myself mistakes left and right too 