GPS

General positioning satellite devices are very nice to have when you're in a a city that you don't really know that well or if you're in a city with a lot of twists and turns. The best brand of GPS is Garmin. They're also the leading brand of GPS used in airplanes.

Since GPS's are so good they are starting to wear down the satellites that were originally sent up. GPS's are also becoming slower because the satellites are not made to be dealing with so many GPS's around the world. Also working on satellites is extremely difficult and expensive; there are currently two satellites down, 8 and 21, out of 30. Now to you that may not mean anything but in the long run it does. It adds alot of strain on the other satellites because they have to pick up the slack of those two satellites that aren't doing anything. By 2050 the satellites will be so slow that they won't even be worth using, because there is such an excess of people using them. 

An interesting fact is every GPS is off by 60-80 feet because of terrorists, they don't want to give the exact corrdinate to anyone who may possibly launch a missle even though 60-80 feet isn't going to mean that much of a difference. 

But if you're looking to buy a GPS the best time to buy them is right befoe Christmas or right after Christmas, because the stores are always having sales.