It wasn’t long ago that luxury cars were available with a cell phone built in. But, for many reasons, this isn’t the future. Instead, with cell phones and, more recently, music players like Apple’s iPod, the trend is to have these devices integrate with the car’s controls and audio system, but not to have them built into the car. Might the same eventually be the case with nav as well?

There are a few arguments in favor of building electronics into the car, chiefly lower risk of theft and no need to mess with cords. The main motivation for the car manufacturers: it’s more profitable to sell an electronic device than a port.

Of course, the last carries no weight with car buyers. And the arguments against built-in electronics are much stronger. People want to simply carry the same device with them all the time, whether or not they happen to be driving. They want to be able to upgrade their technology without buying a new car. And they don’t want to have to pay twice for two different phones or media players, when one will do.

And so, in the past few years, cars have increasingly offered ways to connect to portable electronics as options or even standard equipment. First we had aux-in ports and wireless Bluetooth, the former chiefly used for music players and the latter chiefly used for phones. The aux-in ports were usually free. The Bluetooth cost as much as $700, insane when you consider that Bluetooth earpieces can be bought for under $20. But a car maker’s got to make a buck, right? Also, some nav systems have come packaged with memory card readers, but these aren’t a convenient way to enjoy your music.

Most recently, owing to the success of the iPod, some cars offer full iPod integration. As I understand it, this requires either a proprietary port or a combination of USB and aux-in ports, a special cable, and software to integrate with the car’s controls. As an option, iPod integration can cost $400.

But this is clearly a product of the same line of thought that offered Bluetooth for $700. USB ports are very cheap, and the software isn’t complicated. So once the initial wave of profit skimming passes I suspect that iPod integration will be standard in most cars.