How to link iphone4 via blue tooth to a 2008 prius

It's not possible to obtain stereo Bluetooth for the 2008 Prius. Toyota did not make this possible until the 2010 model with the navigation package. Actually, if your iPhone 4 is jailbroken, there is a complicated way to trick the car into thinking your music is actually a phone call, and it will force play the music over the speakers as such. But the quality is terrible (mono, not stereo). You're much better off sticking to the AUX cable, even though it does get annoying to plug in every time you drive.