A first step on running tests by demand could be to create a Slack bot. We could create a channel on Slack where we can ask the bot to run a test (or compare two URLs), the bot would post the work to our Android or desktop machines, and then when the tests is ready, return the result to the user.
The bot needs to be able to POST a JSON configuration file to our API and then get the result back to the user. As the first step, the result could be a link.