Is your cell phone GPS capable, and does your service provider offer location-based services? Most of them do now. I use VZ Navigator from Verizon Wireless. $10/month service charge, absolutely no maintenance or software upgrades required for your phone, and you'll get to take your GPS device with you everywhere you go. These services provide all the bells and whistles you find on a typical GPS device (voice prompts, visual directions, directory of local gas stations/stores/restaurants/etc.). If your service provider offers a navigation service, I'm sure they'll also sell a window mount for your phone. I love it and will never buy a separate GPS device again.
Wow, verizon charges $10/month for this? You might as well get an unlimited mobile wireless web from them for I think $6/month if you don't already have it, and then just download the Yahoo mobile client. The YMC is free, and if your phone is GPS enabled, you can specify start and end locations using "use my current GPS location". At least you can check your yahoo mail, browse the web too if you're going to be paying for that.
