AppZapp is a free app and service that alerts you when your favorite developer releases an update to an app, or lowers the price on one of its current offerings. If This Then That (IFTTT) is a free Web service that connects a healthy list of services and hardware to one another, making it possible to do some interesting things.
Well wouldn't you know it, AppZapp has a channel on IFTTT, allowing you to create specific alerts for various types of promotions across Apple's App Store and Google's Play store.
I recently created two recipes involving AppZapp, both of which add content to a daily email digest IFTTT sends me at a time of my choosing. The email contains any of the top apps in either respective store are lowered to free. For a recipe pertaining to top apps gone free in the App Store, click here. For the same recipe specific to the Play Store, click here.
Due to the inherent complexities of either store having different listings based on countries and devices, IFTTT allows you to tailor the results to your liking. The two recipes mentioned above are specific to the USA, yet are open to all types of apps and devices.
Naturally with the number of services supported by IFTTT, and the various queries possible with AppZapp, the possibilities are nearly endless. You can view the AppZapp Channel listing for more details on types of alerts, and sample recipes for inspiration. At the end of the day, taking a few minutes of your time to set up a recipe is well worth it. I mean, who doesn't like a free app?