1. Trapster
http://www.trapster.com/
This app is pretty cool because it alerts registered users about potential road hazards in the area. It takes advantage of the mobile phone's embedded GPS system. Some examples of the alerts include red-light cameras, speed cameras, and cops waiting for a speeding culprit. Though I hope everyone obeys traffic laws...(right? :P) I can see this app being very useful on the road, especially in large cities.
2. iNap
http://www.moop.me/inap.php
This nifty app will let you pinpoint on Google map your destination, and will trigger an alarm when you are reaching your stop. This may be useful for buses, trains, carpools, etc. What is better about this app than just setting a regular alarm is it will take into consideration the traffic. If there is traffic, that means you will just end up taking a longer nap until you reach closer to your stop.
3. ShopSavvy
http://shopsavvy.mobi/
This cool app will allow you to scan a barcode of an item in a store and it checks the local area for better deals. It also will check online on the popular shopping sites and will allow you to compare prices so you can get the best bang for your buck.
I wish I had a smartphone...I would definitely get all these apps. They all utilize the GPS system in the phone. I found info on all these apps on this article (http://www.wired.com/gadgets/wireless/magazine/17-02/lp_10coolapps).