iPod & connectivity

An increasingly common feature in aftermarket and factory audio systems is a built-in hard drive for music or photo storage. In new cars, it's currently available from a variety of mainstream and upscale manufacturers.

A few aftermarket units are also available, including models from JVC and Pioneer. Both are bundled with navigation or audio-system upgrades and cost $1,000 to $2,200. Capacity varies, typically between 10 and 30 gigabytes.

Aftermarket and factory radios with USB ports are becoming more commonplace, allowing users to play music files transferred from their home computer or other device to an easily portable flash drive that connects to the port. Some models with Bluetooth allow wireless audio playback from portable devices.

With the ongoing growth in portable audio systems, carmakers and aftermarket car-audio manufacturers continue to offer ways to integrate audio systems with iPods and MP3 players. Many offer input jacks that allow users to play a variety of devices through the car's audio system.

Aftermarket units are also widely available with input jacks and with iPod compatibility. Alpine and Sony, for example, allow a user to operate an iPod using the system's controls and display. Alpine also offers a docking system that allows viewing and operation of iPod menus through a separate display that mounts on the dashboard.

You can also have a car-audio shop install an adapter kit that allows you to play and control an iPod through your current car radio, and sometimes even link it to steering-wheel-mounted audio controls.

Bluetooth technology is widely used for making hands-free telephone calls, and it can be used for audio playback from mobile devices. Advanced Audio Distribution Profile, or A2DP, enables a wireless stereo connection between devices like a cell phone, music player, MP3 player, and a car's audio system. It's available on a limited number of units now. Expect A2DP to be more common in the future enabling you to listen to your iPod or other device through your car system without a wired connection.