Android has various Settings classes, including Settings.Secure, Settings.System, Settings.Global. Within these classes, there are constants. For example, in Android 4.3 and above, Settings.Secure has "bluetooth_address" which contains the BT MAC address. It doesn't exist in older Android versions
Is there a way to find out what constants exist in these settings? I've tried looking at the AOSP source, and "bluetooth_address" exists in BluetoothManagerService.java, which only exists in 4.3 and above under the constant SECURE_SETTINGS_BLUETOOTH_ADDRESS. I guessed that there might be other secure settings using the SECURE_SETTINGS_ prefix, but a quick grep on the AOSP source didn't come up with anything.