Link: https://www.pingbrigade.com/
EDIT: Before I added the monitoring piece, Ping Brigade just had the latency measuring component. One of the users contacted me reporting a bug: sometimes Ping Brigade would tell him that his site was down when he could see that it was not. It turned out he had set up round robin DNS with four web servers and on one of them, apache was misconfigured. I know that this was tiny and anekdotal, but it was nice getting an email from the user saying thanks for helping him figure it out.