A system is provided that enables communications between a driver of a vehicle and a person outside the vehicle, between a rider of a motorcycle and a fellow rider of the same vehicle, or between a driver of a vehicle and another driver of another vehicle. A Bluetooth communication system comprises a Bluetooth communication device mountable to a helmet, and an indicator unit having an indicator disposed in a viewing range of a driver of such a vehicle as a car or a boat. It further comprises a transmitting module disposed in the Bluetooth communication device for transmitting an indication signal to the indicator in response to reception of a calling signal and a receiving module disposed in the indicator unit for driving the indicator in response to reception of the indication signal. The indicator indicates when a call arrives at a Bluetooth communication device mounted on a helmet.