Tunnelmole - https://tunnelmole.com/ . This is an open source tunneling tool in the same category as ngrok. I have turned this into an actual company, it's just a one person one for now. While it is open source, I am trying to build a sustainable business around it. It is bootstrapped and there is no VC funding as of yet. Currently there are several thousand monthly users and just enough paid subscriptions to be making ~$500 (AUD) per month. Promoting it so far has not been too difficult with different strategies, but the conversion rate is quite low, so i'm planning to start doing some data science type analytics to find ways to optimise that.