In this project a magnetic switch turn on/off the power for the Arduino and the Arduino starts. After n notifyAfter seconds the Arduino sends a cmd using a wireless serial interface like bluetooth, TTL-WiFi, etc. A push button can be attached to buttonPin to turn on/off the count down process. A led in LEDPin indicates if the countdown process is running or not. An ESP32 should run a server to receive the cmd that the wireless interface is sending (see related project). ESP32 receives the cmd and plays a massage in a Google device in your home.

• ESP32 Bluetooth Classic with Arduino IDE
• ESP32 Arduino: Getting the Bluetooth Device Address
• Using the BlueSMiRF
• Bluetooth Data Module Command Reference & Advanced Information User’s Guide