We're big fans of Alpine's line of car audio receivers, particularly the mech-less media receivers like the iDA-X305 that we recently reviewed. These receivers have great interfaces and work extremely well with iPods and removable drives, but they don't really offer very many features out of the box. This is where Alpine's line of add-on modules comes in, such as the Alpine KCE-400BT Bluetooth Interface Module.
The KCE-400BT is a hideaway black box that connects to your Alpine headunit via a high-speed, proprietary Ai-NET connection to add Bluetooth connectivity. Powered by Parrot--makers of the excellent sounding Minikit Slim--the KCE-400BT features an external microphone and Active Echo Cancellation technology for clear voice transmission. The additional benefit of using your vehicle's speakers and amplifiers for audio output means that callers' voices come through loud and clear.
Alpine has taken advantage of the addition of Bluetooth connectivity to a car stereo by also including support for the A2DP audio streaming protocol, effectively giving users a bonus audio source for connecting music phones and Bluetooth-enabled MP3 players.
Check out the full review of the Alpine KCE-400BT Bluetooth Interface Module. To add even more functionality to your Alpine receiver take a look at the Alpine TUA-T550HD HD Radio add-on module.