The folks at SeaTurtle.org want to help you find your next iOS device and have setup a web tracker and notification service for Apple's latest iPhone and tablets, including the Retina iPad mini. The online tracker allows you to enter your zip code and select your iPad or iPhone model. The resulting table will then show the availability at nearby Apple retail stores. If the device is out of stock, users can opt to sign up for a notification service that'll fire off an email when the iPad or iPhone model shows up as being in stock on Apple's inventory list again.
The service says it does not scrape the Apple website and instead uses a publicly accessible XML service on the Apple site to determine iDevice availability. It likely adds
