This is an all singing, all dancing bluetooth visor kit. I'm not sure why people but a cheaper one to try and stay legal as you still have to touch the device to answer a call!? The S4 is automated so you don't have to physically touch the device, everything is voice activated and it will even read your text messages. One of the other key points is that it has A2DP which means you can use it as an FM transmitter and stream your entire iTunes library through your car stereo.
Connects and works perfectly with both my iPhone 4 and Blackberry.
Really impressed, thanks.