You may not have realized the benefits of being able to use tweets to find out where your Amazon delivery is, but TrackThis wants to change that. It's an app that combines more than six different APIs in order to let you track your packages over email, text message, Facebook or Twitter. It monitors your packages and when they move it sends you a message with the new location and ETA. TrackThis supports FedEx, UPS, USPS, DHL and other tracking codes.
As you can see in our TrackThis profile, it's a mashup that combines two very different classes of APIs: social APIs (Twitter, Facebook), and package shipping APIs (DHL, FedEx, UPS, and US Postal Service).
As they say in the tag line, it's "Modern package tracking".