Hulk Restock & Back in Stock

Update 24.4.2020:
not recommended for two reasons:
1) they require you to have mailchimp or the other provider in order to actually send the emails - otherwise nothing will happen. I feel that that has not been communicated properly in the product description

2) this is the main reason I am giving a two star review: this app broke my page (due to including jQuery in a weird way). Generally, this is a big weakness of Shopify IMHO - the apps are not really aware of each other and just include jQuery 1000s of times; however this one BROKE the other jQuery inclusions, and I was not able to fix it

On the plus side, the support was quick to answer and clarify about Mailchimp.

I do not recommend this app anymore.

I looked for Notification Apps, and this one made a good impression (mainly because there were no scary reviews of notifications being sent out on accident). It has a dashboard with tracking, showing me which items customers are interested in (which was my goal).

I had to manually install it (modify the theme to add the button) - unfortunately onboarding is not well done when you run the app the first time, it is a bit confusing, the online help was not really helpful when the button did not show up - the code which needs to be added is (just beneath your add to cart button).
This information, fortunately, was present on the configuration screen.

I feel that the text entry fields for configuration of the templates are too small to be convenient - this is possibly something the developer could work on.

The sample notification is sent with an e-mail address "name" which I set, but the actual address is an e-mail owned by the developers. I am not sure what will happen with real notifications, but this is also something I did not expect.

Finally, I am happy with the pricing of this app.