Connect Apple Wireless Keyboard to Raspberry Pi 3 in Raspbian
sudo service bluetooth status # Verify bluetooth is active.
sudo bluetoothctl # Lauch bluetooth subshell.
agent on # [No idea what this does.]
default-agent # [No idea what this does.]
scan on # Displays a list of available devices.
pair XX:XX:XX:XX:XX:XX # This prepares a potential connection, the X's represent your device ID
# A "PIN code" will be displayed, type it on the keyboard and press "enter".
trust XX:XX:XX:XX:XX:XX # Adds device to trusted devices, this survives reboot.
connect XX:XX:XX:XX:XX:XX # Connect to the device now.
exit # Return to previous shell.