Its cool how the GPS shows your location on a google earth map with streets. You can type in where to get from one location to another. It shows you the direction. But it would be cooler if there is a voice navigation, so when you need to turn right or left, it would tell you. I would just get a GPS navigation, but why pay more if sony can just put it in on the vita.
There are literally hundreds of gps nav apps on the iphone. From free to around $80.
Not sure how handy a nav app would be on the Vita, since noone (yet) makes a car mount for it. The Vita would be a little awkward to hold while driving. Directions on Google Maps are convenient because you can view the entire route before you get started. With a GPS Nav app, it only tells you to turn when you are approaching the next turn, which means the app needs to remain active (and therefore burning through your data) for your entire trip.