I wrote a program to automatically generate class diagrams, filtered by coupling. Here is the result for CoreBluetooth in iOS:
You can see there are clusters around CBPeer, CBPeripheral, and CBCentral and that CBCharacteristic is another class with lots of references.
Obviously, huge class diagrams are more noise than signal, but if I further filtered this down to specific topics...?
I dunno'.
P.S. Yeah, yeah, they should be open diamonds, not filled diamonds.