I think it's quite a nice idea, but I'm struggling to imagine myself using this. For a start, I want my tests in my source code repository. Secondly, I want to run my tests locally before I upload to production, perhaps even before I write the code to satisfy the tests.

I see that you have also developed a chrome extension so that one could run their tests locally. But that is essentially different from running your tests as a service. In this case you're essentially providing a testing library.

I could just about see myself writing my tests locally (perhaps using your chrome extension) and using the local tests for development and then uploading those tests and using a service to check a production server periodically. But I'm a little sceptical (why not just have the production server run the tests periodically itself?)

There may be some other uses for Web UI Automation as a service, for example scraping.