I wrote about location-centric devices in the car a few months back and how you may some day be driving along and up pops a banner ad of sorts on your navigation screen. Or who knows, maybe the ads on your radio will be customized based on the businesses you are currently driving by.

The technology already exists. The Matrix will soon know where you are. And maybe whether you like it or not.

Customized advertising may be the least intrusive application of location technology.

There are already black boxes in passenger vehicles that gather data on throttle position, speed, steering angle, brake application and other data that can and have been subpoenad by insurance companies and in court.

Its not a stretch to think that these boxes will soon gather, store and maybe even report location data without your knowledge.

In the mean time, Yahoo would like to make use of it now, and at least for now, will ask for your permission.

Yahoo knows where you are

On Tuesday at Yahoo’s San Francisco-based skunk works – known as the Brickhouse – the embattled Internet company unveiled a new location services platform dubbed Fire Eagle.

Location is one of those things that has huge potential for adding a layer of context to all kinds of services on the Web.  Geo-tagging – the practice of adding geographic information to Web sites, photos and videos – is gathering steam across all sorts of Internet-based properties, from restaurant review sites to social networks and house hunting services. What has been missing, however, is an easy way to insert yourself into that growing stream of geographic information.

In essence, that is what Fire Eagle does. You either tell Fire Eagle where you are, or give permission for some device to do it on your behalf – say your mobile phone –  and Fire Eagle broadcasts your location information to the services that you have approved.

Which all sounds cool, and there may be some constructive, relevant use of this technology for consumers – as long as they retain the right to turn it on and off. I have Google Maps on my Treo, but at least for now, you have to tell it where you are. Equipping it to automatically know where you are would be useful.

“Where’s the nearest Caribou?”

So imagine that all your friends on Facebook now get feeds on your location, by city, neighborhood or even street address. If you are driving through a neighborhood house hunting, you could get updates on homes on the market, past sale prices and upcoming open houses. Hungry for Italian? The closest places for a decent plate of pasta come streaming to your phone. Note that you can do much of this today with individual services, but you have to tell each of them where you are. With Fire Eagle, you give your location once, and all kinds of services can access it (again, only with your permission).

If advertisers know where you are, they can entice you with deals/coupons/menus on the spot.

Apple is in on it as well. No surpise there.

Yahoo will face competition from the likes of Apple (AAPL), which has made scores of location-based services available as downloads for the iPhone, and Google (GOOG), whose Android mobile phone platform is expected to do the same for a range of mobile devices.

“No Elizabeth, I’m not at Rielle’s place again. I promise.”

In every case, whether it’s a social network or an advertiser, a person’s location will only be made available to those services that individuals approve. And if you don’t want anyone to know where you are – illicit affair, job interview – you have the option of hiding your location for a period of time you determine, or even lying.

“We think it’s a good idea that users can lie about where they are,” says Tom Coates, head of product at Yahoo’s Brickhouse. “Like I don’t always tell my mother where I am.”

Repeat after me:

You can’t get away from the Matrix. The Matrix always knows where you are. You need the Matrix.