If you are talking about creating webhooks on other devices through an rpc http channel, yeah you could do that, but its not working the way it should work, for example a gen 1 shely need a different syntax for a webhook than a gen 2, and there are different webhooks for different types of shely, as well as some harsh endpoint limitation. I tried to make an easy to use tool out of this, but there are just too many variables.
So, thats why I created the simple webhook script as a workaround, for now, maybe i will give it a try a bit later but right now the simpel webhook script is good enough to solve this problem.
--> deviceIP/settings/relay/0?out_on_url=http://localhost/relay/1?turn=on
No idea what you heard, but this syntax would never work on a gen 2.
First of all a Webhook is called action insde shellys, and thats just a link { endpoint } you connect to a special event { relay turned on } that you shelly will call when that event will happen.
If you are only using gen >=2 you could try the remoteEvent function from my toolbox, that was my first try to create action, webhooks and endpoints automatically, but like i said its not working right, you should stick to the simple webhook script, and just create the Action your self, over the Shelly web ui on each remote Shelly.
So to answer your question, I need some more specific information or just stick to the simpel webhook script.