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
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...?
P.S. Yeah, yeah, they should be open diamonds, not filled diamonds.