I'm a developer who's been trawling the Shopify community forum looking for app ideas. I discovered that a vast majority of requests seem to be for notifications of some sort - inventory changes, order updates, and so on.
With this in mind, I was thinking it would be super simple to let store owners build their own notifications where they could decide what store events they want to be informed about and how. Of course, you will be able to build these notifications with writing a single line of code. Pricing will be pay-as-you-go but compared to Zapier, it will be pennies on the dollar.
Any interest in such a self-serve notification tool?
This may be a good idea to follow. It is useful and bumped into it several times.
However, Shopify Flow may have a similar functionality. It is on Plus only I believe so there still can be a market out there.
Best of luck!