I would also like to see this bluetooth receiver support.
I have been looking for a device I can have connected (wired) to my amp and speakers, which I can connect to via bluetooth or AirPlay from my phone and stream audio from the phone to the device for playback. There are many options for Airplay only (like M2P in it’s current iteration) and there are many devices that do bluetooth to RCA out (Logitech makes one for US$25) but I have not found anything that does both.
Now that the RP3 has both bluetooth and wifi built in, M2P has shairport already, and the bluetooth addon exists (albeit only for broadcast), I hope this can be something that can be added in without too much additional effort.
Unfortunately, Airplay is only on Apple products. By adding the bluetooth playback option, any guests to my home, with either Apple or Android devices, could easily connect up to the system and play their music.
I don’t know anything about programming hardware/software drivers and interfaces. I did find that someone had put this together already on an RP2, so he had to use 3rd party bluetooth hardware and software. The comments on his Instructable indicate that with the RP3, none of those 3rd party items are necessary, and also that the scripts he provides don’t work. However, it may provide a good jumping off point if it is decided to look further into this feature, as I hope happens. The old directions can be found here: http://www.instructables.com/id/Raspberry-Pi-BluetoothAirplay-Audio-Receiver-combo/?ALLSTEPS