OpenGarage is an open-source, universal remote controlled garage door opener
What I really like about this device it is universally usable. Unlike some remote garage door controllers which are only compatible with certain brands, OpenGarage is able to open or close the door remotely, determine whether the door is actually open or closed, and even whether your car is parked in the garage or not. It connects to your router by Wifi and their mobile app for iOS or Android (a Blynk app) will provide status and remote management functionality.
How it does this is quite simple but clever and it utilises two basic functionalities when the device is mounted on the ceiling pointing downwards):
1. Distance detector - from above it knows the distance to the floor (no car and garage is closed), to the car roof (car is in and door is closed), and door when opened.
2. Relay - to simulate a button press on your garage door remote. If your garage door motor unit has terminals for this it can connect there, but if not you can solder the wires to a spare remote's button and let the remote sit next to the unit (universal!).
Apart from the mobile app you can also control this device via IFTTT or even the Home Assistant service.