Este script básico fará o trabalho:
#!/bin/bash
status=$(nmcli -t -f WIFI nm)
if [ $status = "enabled" ] ; then
notify-send -i network-wireless-disconnected "Wireless" "Wireless disabled"
nmcli nm wifi off
else
notify-send -i network-wireless-none "Wireless" "Wireless enabled"
nmcli nm wifi on
fi
exit 0