[Fandonov] has created a weather station project with an Arduino Uno at its heart and a Waveshare ... aside from Arduino and display it boasts an Adafruit sensor board and a hardware clock.

There’s a huge market for 433 MHz alarm system hardware out there, from PIR motion detectors to door and window sensors ... ESP can fire off using whatever API works for your purposes.

Connector to add external battery to real-time clock (RTC) inside Renesas MCU (MCU RTC power pad held to 5V rail on Minima) Secondary (wireless) processor: 240MHz 3.3V dual core 32bit Espressif ...