What Bluetooth profile/protocol is used for a carkit to know the signalstrength and/or batterylevel of connected phone

Question

I have Bluetooth embedded in my car its default mediasystem. When my phone (Nexus 4) is connected it displays the signalstrength and batterylevel of the phone on the display. What Bluetooth profile/protocol is used for this? I've investigated the HFP and MAP profiles but couldn't find anything on signalstrength or batterylevel.

In the end I want to make an Android app which sends the batterylevel to the car its Bluetooth 'carkit' to enable a charging 'animation'.

Answer 1

Most probably this is using Hands Free Profile (see sections 4.5 and 4.7), where the Audio Gateway (your phone) can report both signal strength and battery level to the Hands Free (your car).

I'm not familiar with the internals of Android, but I would imagine the Audio Gateway is part of the platform and not programmatically modifiable - here's no good reason to let a developer modify the battery or signal strength being reported to other devices.