LAS VEGAS -- Music got truly mobile at the Consumer Electronics Show this year, as a number of car manufacturers and car stereo makers finally got serious about including digital music apps into their products.

The vast bulk of the activity lay in the after-market car stereo space. There wasn't a car stereo manufacturer on the floor that wasn't displaying at least one unit branded as Pandora-ready. That's the result of an effort on Pandora's part called Pandora Link, a set of APIs that the company has made available to device manufacturers allowing them to add a Pandora user interface into their units.

They include Pioneer, Kenwood, Alpine, Sony and many more. To give an idea of how far things have come from just last year, consider Pioneer, Pandora's first car audio partner. Last year Pioneer displayed two Pandora capable units, starting at $1,000. This year it had nine, starting at $150.

Among the more creative implementations was one from Oxygen Audio called the O'Car. Like a radio head unit with a removable face, except the iPhone is the removable face, the O'Car turns the iPhone touch screen into a tuning unit. Just snap it into the unit and users can tune FM/AM radio via either the knob on the unit or the touch screen of the iPhone. Radio preset buttons are on the iPhone face. And best of all, users can stream music from any music app on the iPhone through the car stereo. The only downside is that it requires using the phone interface rather than one designed for in-car usage.

Including access and Pandora to the car will really take off once car manufacturers include them at sale. Along those lines, Ford and Toyota led the way.

Toyota introduced its Entune system, basically an in-dash collection of apps that include Pandora and iheartradio. While the apps reside in the car, it requires a Bluetooth connection to a smartphone running the Entune app. All smartphone platforms are supported. The system was created by Denso. Exactly which makes/models of cars that will contain the system being announced at the Detroit Auto Show next week.

Ford revealed that its Sync voice controlled system has been built into 3 million vehicles since it launched in 2007, and has updated it so that all include access to Pandora. Also, Sync is expanding from the Ford Fiesta to becoming an option for the Ford Mustang as well.

Meanwhile Audi will be joining them soon. The company announced during its keynote an initiative called eSolutions, designed to incorporate the best information and entertainment apps and install them directly into Audio in-dash systems. No mention whether music will be part of that, but it's certainly expected.

Other car makers may jump on board, given the interest in the space by the OEMs that make their in-car units. Visteon is one such company that showed off two new music integrations. Two years ago it announced support for Pandora -- one of the first to do so. Last year it added Slacker. This year it added the first on-demand service in MOG.

It also debuted TerreNet, a car radio that combines Internet radio with terrestrial radio, and brings Internet-like personalization to terrestrial radio. Users create a profile that includes what artists they like. The service then lists local radio stations that play those types of artists. For long drives, will list the next city's radio stations playing the same genre.

Driving all of this innovation is the smartphone. Besides carrying the music apps needed to play on most of these car systems, they also provide the Internet link needed to access them. The tighter the integration, the more the interface of these apps have been optimized for in-car usage (think voice control, or more simply touch screen) to that it creates a minimal distraction.

"When we thought about cars, we didn't think it would go this fast," says Pandora founder and chief strategy officer Tim Westergren. "Smartphones shortcut the whole process."

And according to Westergren, next year's growth spike will likely dwarf what we're seeing this year once drivers with these systems start showing them off to their passengers, allowing the to word spreads virally.