Video
Streaming low-latency video is a challenge for firewalls and VPNs, and Knocknoc is an excellent solution.
The ipset backend script is a great tool to allow things like SRT or RTMP to select IPs.
The Knocknoc demo includes an RTMP example, where the backend updates an IPset as the users login and out. This allows the video stream to play and stop as required, providing a solution to access control where none-existed before.