A quick test using Zapier's webhook functionality tells me I can duplicate this with their platform. Doesn't seem to work with link shortener, but I have the sense more time invested on that will yield a result. So, I think the concept has merit but you're off center of the target and much more value is required.
I imagine there's a lot of value to be found in a dashboard, or generally in managing these canaries. Which canary was deployed where, how often are they triggered (with the ability to mark some instances as false alarm) etc.
But of course that heavily depends on the use case