Dayon! is an open-source and cross-platform (JAVA) solution that allows watching and controlling a remote computer. In this sense, it is very much similar to existing remote desktop solutions.
But I guess it's got some features that makes it valuable.
Easy SetupDayon! is dedicated to people who are quite new in the computer world. There's no need to set up the network (i.e., no firewall setup, no router configuration, no NAT setup) on their computer. Dayon! is acting there as a client connecting to the monitoring computer.
Low Network BandwidthDayon! is sending compressed and cached gray (up to 256 levels) pictures to minimize the network usage offering as much as possible a real-time experience over the Internet. Those pictures are far enough for monitoring and explaining the different menus, icons and discovering the computer setup, etc...
You'll find more details on the official web site for Dayon! https://retgal.github.io/Dayon/