As a helicopter pilot, you often fly close to terrain with limited vertical maneuvering options. In addition, visibility is often limited and you share the airspace with other aircraft in the same situation. Obstacles are also an issue and can easily wreck an otherwise successful flight.
PowerFLARM can alert you not only about other FLARM equipped aircraft, but also transponder and ADS-B equipped aircraft. Moreover, the optional obstacle collision warning system tells you about obstacles that were just not visible enough.