Back In Stock,Notify Me: Kbite

Great app, reasonably priced with plenty of tier options to suit your needs, and A+ developer support. After installing just to give this a try, I was contacted by Sam at CartBite welcoming me, and offering to switch the Notify button from a floating sidebar to an inline layout that shows up under the 'sold out' blank add to cart button. Polite, fast, and effective.