Most modern day cars already have some form of Bluetooth integration. What this means is that instead of strapping on an earphone, you can receive and make calls using the car Bluetooth speaker. But in case your car is slightly older or doesn't have an in-built Bluetooth, you can always invest in a Bluetooth speaker for car that will free your hands and help you concentrate more on the road, less on the phone.
Here's how this works: if you get a call on your cellphone, you can use your Bluetooth headset to answer it. This is comparatively less distracting than answering a phone directly. But a lot of people either don't like using headsets, or find that it distracts them from driving. Consequently, most modern cars come equipped with car Bluetooth speakers. These are typically built into the steering wheel. When you receive a call, you can either press a button (located on the steering wheel), or use a voice command to answer or reject it. This frees your hands completely, and distracts you even less from driving than a standard headset.
If your car doesn't already have Bluetooth integration, you can buy these speakers separately and hook them up to your steering wheel. Most of these speakers will feature a microphone and a speaker (for calls), a LCD display (to show you who is calling), a SD port (to save MP3s) and a USB port (for storing anything else). A Bluetooth speaker for car can also double up as an MP3 player or USB drive. Some also have a FM transmitter built in.
Many Bluetooth speakers for cars are battery operated, while others depend on a power source (typically the car's cigarette lighter). The latter is not a highly recommended option since you will essentially be tethering your steering wheel with a wire, which, despite whatever precautions you may take, is definitely a safety hazard.
If you are the busy professional who can't afford to miss out on calls when on the road, investing in a Bluetooth speaker for car should be a priority. It significantly reduces the risk of accidents and makes for a far smoother and seamless experience. No more fiddling around with headsets and cellphones; simply speak directly into the steering wheel to answer calls. Plus, your speakers can double up as a USB drive, a MP3 player, and a FM transmitter as well. If that isn't high-tech, then I don't know what is.
Motorola's T505 ROKR Bluetooth in-car speaker comes highly recommended. It has everything you would want in a Bluetooth speaker for car. It fits right on to your steering wheel and lets you make and receive calls directly. It announces the name of the caller, features a full-fledged FM transmitter that announces the name of the station, is rechargeable (can be charged in the car itself), and also includes a MP3 player. Another device to consider is the Jabra S500, which is a cheaper alternative to the Motorola T505.