If you have power (5v) at the button location, you can just build a box with a doorbell button on the outside and an ESP8266 (wifi enabled) on the inside. Load it with Hubduino software and you can have a device in HE which will change status when someone pushes the button. HE can then alert you through one of the standard Notification devices. There is a deep sleep mode on ESP devices which may let you get away with running it on battery.
Download the Hubitat app
