In my car I have my old Android phone as the GPS and music player. I was hoping to use it as a receiver for my calls coming to my other phone and any bluetooth devices around it streaming music. Is there a way to do this? I have searched Google thouroughly.
Technically it is possible with most Bluetooth Android phones but you would have to root your device and find a ROM with source code like
CyanogenMod and rewrite the Bluetooth driver.
Unfortunately there is still no bluetooth server implementation available for android devices.
You need to connect your devices via "WiFi direct" or the portable hotspot of your device. Then you can use your old phone as wireless speaker for your main device. The app also supports google music and online radio stations.