I think we need to make a highly-available downdetector from a collection of SBCs hosted around the world. Each node gets its configuration via git-pull which is self-hosted/republished. Simplest DNS configuration possible: each node has a unique $n.isdowndetectordown.ultradowndetector.com while they also happily host a common hostname with simple dns round robin entries for it.isdowndetectordown.ultradowndetector.com. The common page attempts to load a check resource (perhaps just a tiny css output?) from all of the $n.i.u.c nodes which just changes a div from gray to green/red.

It would be interesting to see just how small this whole thing could be; I bet it could be made into a <500MB sdcard image for a RaspberryPi4/2GB that simply updates a static css out of (say) cron and serves a surprising number of HN requests.

With all of this redundancy, there is no way it could fail! /s