This is a Call Notifier application involing android and arduino. When a call comes to your mobile phone, your wifi MAC address will be sent to your arduino. My idea is that we can identify each mobile phone with its unique MAC address and each mobile phone can be differentiated with the MAC address. You can modify the Arduino code accordingly to your version of the app. You have to change the IP address in your android code according to the IP assigned by your router to the Arduino wifi module.
Enjoy and Be Well!