Jetspotter is a simple program that queries the ADS-B API. It is used to send notifications if a specified type of aircraft has been spotted within a specified range of a target location. If one or more jets have been spotted, a notification is sent. The notification contains some metadata about the aircraft, a picture fetched from planespotters.net and a link to track the aircraft. A notification is only sent once for each aircraft. If the aircraft leaves your maximum configured range for at least 1 fetch iteration, a notification will be sent again as soon as it enters your maximum configured range.
Please have a look at the documentation for installation and configuration steps.
There is a demo of the web interface available that shows aircraft in the vicinity of the Brussels airport.