The most amazing piece of technology I have owned is not my T-Mobile Wing, not my Directv HD, not my Garmin 60Csx, nor my iPod Nano. No, the most amazon thing I've ever owned is a gift from my folks last Christmas: the Celestron Sky Scout.
This thing is un-friggin-believeable! It is touted as a personal planetarium, and its just that. Want to know what that bright (or not-so-bright) object is in the sky? Look through the viewfinder, find the object, and press "target." The Sky Scout tells you what it is. Want to find a star or planet or galaxy? Use the intuitive user interface to select the name of the object you want to find. The Sky Scout then gives you directions through the viewfinder to find your object, using arrows to move you in the right direction.
Looking for a constellation? Look it up, and it will show you all the stars in the constellation, allowing you to trace it. It also provides deep descriptions of each star, constellations it is a part of, and layman's terms on how to find it (e.g. "the third star in the big dipper's handle").
What's amazing to me is that it simply works! It uses GPS, and will take a couple minutes to fix on the GPS satellites. From there, given the time of year and the angle you are holding the device, it knows what you are looking at. Amazing.