I don't know why but every time I've heard about this type of monitoring I'm somewhat in awe of it. Like it makes complete sense but I'd never heard of it until the pandemic and it seems like an extremely useful but also non-invasive monitoring system. Even "cooler" it's been around for over a hundred years (obviously in cruder forms but still same concept).
The folly of admitting people from Polio endemic areas without adequate screening and without mandatory vaccinations.
It’s in the Orthodox Jew community and it’s origin is the polio vaccine (weakened virus). Sometimes it reverts to not weak.