Your car PC and car speakers can act as a hands-free unit for your mobile phone, using Bluetooth wireless networking.
Bluetooth is a low-range, low-speed, and low-power radio frequency transmission protocol designed for attaching peripherals to computers. You can think of it as a sort of wireless alternative to USB, just like WiFi is a wireless alternative to Ethernet.
One of the "killer applications" of Bluetooth technology is making mobile phones hands-free, either through a wireless headset or by direct integration with your vehicle. And while only a few of the newest cars come with Bluetooth hands-free capabilities built in, your car PC can speak Bluetooth and integrate with your mobile phone, no matter what kind of car you drive.
In order for your car PC to act as a Bluetooth hands-free speaker, it needs to make a wireless connection to your mobile phone. To enable this, you need a Bluetooth interface (a.k.a. a dongle; see Figure 6-2). The most common interface used for Bluetooth dongles is USB. Some manufacturers have a serial (RS232) interface, but this is unusual. For a car PC, the tiny USB form factor is excellent.
Figure 6-2. A Bluetooth dongle
Bluetooth is fairly standard. Most of the dongles are based on a Cambridge Silicon Radio (http://www.csr.com) Bluetooth microchip. Pretty much any standalone dongle you purchase ...