How to use Android device as a bluetooth headset for another mobile phone?

Question

I want to make my android device working as a bluetooth headset. I search the Android APIs, but I just find some interface which can make Android device working as a masters, not as a device(bluetooth headset). I'm also ready to modify the source codes of Android OS, and rebuild the OS. What I hope is, when Android devices connect to a mobile phone with bluetooth, the Android devices can work as a bluetooth headset. I don't know whether there are interfaces can do this, or I should modify the Android OS? Thank you!

Answer 1

You need to implement HFP profile in your android device, normally phone role is AG(Audio gateway) and headset roles is HF(Hands free) , think its as a server and client role. Connect RFCOMM channel to phone using UUID defined for HF , have SDP record updated,changes will be required to handle AT Commands as well. These will be the initial changes, once done you will need to handle audio packets(SCO packets) for voice calls