It is a serial terminal that runs in the browser. I thought of it again when I asked someone to send M122 and they only had a MAC. This should work with chrome, at least, and the developer uses a chrome book to talk to his printer with this. I think the web serial api has been added to a few browsers now.
Maybe this is a decent alternative for RH, since it is kind of a lot to handle some serial comms.
Anyone want to try it?
Also, this is all the code for that site. Amazing: