Widely used for mobile phone, which support Bluetooth.
Answer calls via Bluetooth gear, away from mobile phone radiation.
Answer calls without taking your phone out of your handbag or pocket.
While you are relax on sofa, playing games, do hand-working, just leave the cell phone on the table or anywhere, free your hand for meeting, holding umbrella.
Receive calls when driving, more safe.
Music playing: to enjoy music everywhere.
Ringing to get a reminder of coming message, Skype, Whats app, etc.