I've talked to a few dozen people in web development to try to figure out if other people would find this useful, though most of the feedback has been that performance is more of a "nice to have", and that their company is more worried about releasing features.
Am I just talking to the wrong people HN, or do companies in general not care?
Don't let that discourage you. $29 month is a reasonable price for the number of tests, especially for companies. Charging annual makes sense at the early bootstrap stage. (Our smallest plan is $50, we loose some customers, possibly to the competition but we target B2B primarily).
Website https://perfbeacon.com/ looks good, add more features and content, improve in small steps, marketing of course and just be patient until the customers come.
I'm following https://twitter.com/sinequanonh on Twitter and it's amazing how every small step seems to bring in more revenue. (His service that pings websites and reports latency performance)