Here's a website performance tool I discovered today that tests your website speed from 18 servers around the world at one time.
It was built by the company Wordfence as an internal tool to measure the performance of their own site, because there wasn't an existing tool that could do the job. Other sites like Pingdom Tools and GTMetrix only let you pick one server at a time to test form. Wordfence built it for themselves and then later made the tool public.