Notify! Back in Stock|PreOrder

This app is basic but does exactly what it is supposed to do, and does it well. I like that the widget, notifications and text can all be edited, and discounts can be added to the email. More importantly, the customer support is available by real-time chat, is responsive and helpful. They changed the look and location of the widget for me and suggested other enhancements to the customer experience. That's key since it means getting help quickly instead of sending an email and waiting for a reply in 1-2 days. Fixes with this type of app usually need to happen quickly.