Which applications notify when a site is available?

Question

Android

We need an application for Android, which once a minute or at least once every five minutes checks if the link vk-mm.com/serve/config returns an error with a code greater than 400. I found one that suited me - it beeped when the site was unavailable, but only when it was active, i.e. background didn't work

Answer 1

uptimerobot.com+pushbullet is
the first one that monitors site performance and sends you error messages through the second one.
on the free plan, uptimerobot checks once every five minutes (or less often, it doesn’t do it more often).