Use "Sleep Mode" on/off as a trigger for a Shortcut?

My goal is to inform my Homey about my sleep status.

Since the last thing I do before going to bed is enabling “Sleep Mode” on my Apple Watch (and the first thing when I wake up is disabling it) I was hoping to use that as a trigger to send a webhook, but that trigger does not seem to be available in a Personal Automation?

Any other ideas how to achieve this?