During the excellent Modern Endpoint Management summit in Paris, I was sitting in the equally excellent session from Florian Salzmann and one of the questions was if the Device bulk commands could send an on-demand remediation to multiple devices and the answer was no.
This gave me an idea so I built this script on the fly.

It will prompt to select a remediation and then select any devices, click OK and it will run that remediation against any and all devices selected.
Of course, it supports parameters and app registrations too.
You can grab it from GitHub here
Or PS Gallery Here:
Install-Script -Name bulk-run-remediation-ondemand