For cell phone safety, most people use hands-free kits for convenience and in some parts of the world it is the law to not drive a vehicle when talking or texting on a cell phone. Some people will use a hands-free kit because they are concerned about cell phone radiation.
However, scientists and consumer groups in Europe have done studies and tests regarding hands-free kits and found that the wire from the ear piece act as an an aerial and it increased the radiation by three times. The Bluetooth headsets are just as dangerous because the signal from the phone allows the radiation to travel directly into the inner ear.
For your cell phone safety and your health you need a device that has been solidly tested and tried and decreases up to 97% of the harmful cell phone radiation.