GCPing measures latency between your browser and various GCP regions around the world. It makes HTTPS requests to Cloud Run services running in each region and displays the median reported latency.
After four and a half years as my personal side project, gcping has been taken over by some remaining googlers and moved to https://github.com/GoogleCloudPlatform/gcping
This is still not an official Google project.