TL;DR recently Microsoft Teams managed to disable the ability to call Emergency Services (911, 999.) While Microsoft’s product was to blame, and a new version of Teams is available that fixes it, it’s an obscure Android bug that was triggered and can be triggered similarly by other apps.
The checker is a downloadable APK that counts how many phone registrations are taken by any app and will let you know if it’s absurd. Android itself will be patched against accidental app exploit/abuse but that’ll be a month or two off before it releases to the wild and then who knows how long it will be before your phone manufacturer pops it in.
It’s probably not a huge issue, but you can at least tell by downloading and installing that apk whether any apps have registered hundreds of registrations and managed to bottleneck your ability to make emergency phone calls.