I built this because I kept checking Google Flights every day for the same routes. FareBot is a Telegram bot you host yourself that does it for you and your friends.
Runs with Docker, no API key needed. It's meant for you and a few friends: anyone else who messages it sends you an access request.
One I found with it: Budapest to Venice for €17, 83% below usual:
Limitations: Google Flights has no public API, so if Google changes the page it breaks until I update the parser. One-way flights only for now.
Feedback welcome!