It is full set harness no need to tap or connect any wire. 

Video installation is available on Youtube chanel. 

It is designed to support passengers safety when driver got to leave the car during travel but passengers do not want to get off.

It will function only when seatbelt of driver side is unplugged, meaning dirver is not in the car. And it will not work if seatbelt of driver is plugged in, meaning driver is in and car is running for safety reason.