I would be happy to pay for the product or just pay someone to build it if it isn't hard.
Here are my assumptions: 1. I could enable this on a cheap cloud server to expose a terminal that will work with tmux and vim. 2. I could create an account for my friend(s) so that they could access the server securely from within thier browser. 3. There is no clientside install or config needed.
Let me know if you are willing to wire it together.