Any good electrician can install it.
The DC control parts goes to the ACC ( or accessories) power line, so it will send an on signal when the key is on acc ( when the radio is on, windows goes up and down but motor is off).
The relay part goes directly to battery, so when you turn off ACC the br1 is still on and draining until the time goes off. After that the relay shuts down, and br1 goes down.
If you turn back to ACC ( or turn on the vehicule ) then the relay turn on again and br1 start powering up.
I dont think BR1 should come with something like this. It add complexity to a communication device and I think the double power source ( terminal block and 2.5 mm plug ) is verstatile enough to build your own power supply strategy ( like this shutdown delay timer ).
If u need more help please PM me, I have done some interesting things with some microcrontrollers and relays for BR1 deployments.