Some locales prohibit the use of cell phones while driving. The Personal Device Interlink avoids that by providing a Bluetooth connection to your phone via a small headset.
A small button on the side of the headset of the model PDI-B902/MAH connects and disconnects the call. 
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Those who are fired with an enthusiastic idea and who allow it to take hold and dominate their thoughts find that new worlds open for them. As long as enthusiasm holds out, so will new opportunities.
I think headsets are better for a lot of reasons, and driving better is definitely one of them.