It looks like the United States Postal Service is considering all its options for how it handles mail in the future, with it even go so far as to commission a GPS tracking system from TrackingTheWorld Inc. Among other things, the USPS apparently required the system to be able to report the position of a piece of mail at customizable time intervals, record down time, and interface with Google Earth, not to mention fit in a standard size envelope. From the looks of it, it appears that TrackingTheWorld manged to meet all those considerations, producing a system that's just a quarter of an inch thick and the size of a tri-folded piece of paper. What's more, the system also boasts a microSD card slot that allows for "future extended tracking missions," and it includes a slim 1100mAh battery that promises to last for 20 hours in a timed configuration, or up to two weeks in "tilt mode," which only kicks the system into gear when a tilting movement is detected. According to the company, the so-called "Letter Logger" should be ready by February of next year, although it obviously won't be available to the general public. You can always build your own mail tracking system though.