As I just learned, apparently you can make HTTP requests from postgres like so:

    copy (select 'hello world') to program 'curl -m 10 --data-binary @- https://some-url-here';

There's also a postgres extension for making HTTP requests but this seems to work out of the box (if curl is installed).

The "-m 10" parameter is 10 second timeout, to reduce the risk of this command hanging. I did not test what happens if curl returns non-zero exit code, this would also need to be tested and handled.

One could use this to monitor pg_cron tasks with external cron monitoring services. I'm not sure if this would be overall good idea, but one could :-)