Espressif’s ESP8266 Wi-Fi module has been used for many different projects that range from a wireless web server to appliance automation and everything in between. While it can be integrated into a boatload of complex projects, it can also be used for simple tasks as well, such as sending push notifications when an action is triggered. That’s the idea behind Kevin Darrah’s (KD Circuits) trigBoard, which does just that using a digital input, almost like Amazon’s Dash buttons, but more straightforward.
Darrah designed the trigBoard around the ESP8266, which spends most of its time asleep to save power until it’s needed. A low-powered (35nA) Texas Instruments TPL5111 Nano Timer wakes the ESP8266 hourly to check the battery’s status (power levels) and features a manual wake pin that’s utilized to trigger actions based on external input garnered from sensors.
The module offers a pair of Micro JST connectors, one for a Lithium Polymer 3.7V battery (that charges via micro USB port), and the other for whatever sensor or switch you want to deploy- such as magnetic switches (for tripping openings), motion sensors (movement trigger), or temperature (alert for fire), and a host of others.
The firmware for the trigBoard is set up to use the Pushbullet app, which sends the push notifications to the smart device (iOS, Android, Windows) of your choice. Darrah breaks down the entire trigBoard makeup on his project Wiki page, which also hosts its schematics and code as well for those who would like to make their own; otherwise you can purchase the board on the link provided earlier.