XFlow Back in Stock Alert

Finally, a professional grade app with professional support to back it up. I have never received the level of support I've experienced with this app in any other I've tried; they seem to be around almost 24x7 and most issues I've raised get solved on-the-fly by their support team with direct integration to your store. It does exactly what is says it will and is being actively developed with community discussion to hone its feature set. Kudos to a job well done.