If you plan on using a  Car GPS in the same vehicle all the time.

A built in GPS is a clean and neat solution, but check out these details before you buy a preinstalled unit or try to install one yourself.

Many new vehicles have built in GPS systems available.  The good thing about this is that it is all tucked away.  Nothing to clutter up the interior and get stolen.  The GPS power system and antenna are more stable, just like a built in cell phone.  The downside of a built in GPS system is that you don't have a choice in the technology.  The brand and software available in the car you are buying might not be what is best for your kind of driving.  Also, the data on the system could be obsolete.  Make sure that you bargain with your dealer to include at least one update for the software. ( This will be a disk, like a CD that you insert into the unit box, usually in your trunk.)

If you are upgrading your current vehicle you have more selections, but are limited by the space provided for your radio.  Look in your car manual for the dimensions and specs, and bring the manual to your vendor before buying your GPS unit.  And yes, some GPS systems can have radio and MP3 features.

Another thing to watch out for with a built in car GPS system is how it gets its positioning data.  Some car GPS systems are run off of cellular phone services rather than satellite receivers.  This may not make much of a difference in a well serviced city, but will do you no good in tough terrain such as mountain passes.  See the section on choosing a GPS service for remote areas to find out why is this important?  I'm going to give you two tragic personal experiences.

The first one was when we were driving across Oregon.  Deep in a mountain pass, a car was pulled over and the driver was stretched out, on the side of the road, having a heart attack.  A good Samaritan was giving him CPR but he needed a paramedic team as soon as possible.  Cell phone signals did not work down there.  Luckily, someone had a GPS device and locked the location in it.  Then they drove up out of the pass and got a cell signal.  They could then tell emergency services exactly where the heart attack victim was located.  As we drove to the nearest town the rescue vehicle blazed by us confident in where they were going.

Another time we were travelling across a mountain pass and saw a car in the oncoming lane had smashed into concrete lane guard.  Our lanes were separated by a ravine and there was no way to stop and help.  This time we could get a cell signal but didn't have a GPS system with us.  We called 911 and went through several frustrating minutes trying to describe the exact location.  Fortunately I knew the highway and could give them an estimated travelling time from the nearest town, but most people would have no idea of where to tell the dispatcher to send help from.  IF I had a satellite GPS device I could have just locked in the position and passed on the information, but with a cellular GPS I would only have been able to give a general area, since the cell towers are run in a string through that area, making triangulation impossible.