Your car could soon be just another "device" on your Mobile Share plan, if you're an AT&T customer and happen to own a GM vehicle.

The carrier announced on Monday that it would soon begin supporting LTE on select GM cars as a $10 add-on to AT&T Inc. (NYSE: T) Mobile Share data plans. That's the same cost as a smartphone or a tablet addition, and it'll give drivers 200 MBytes of additional data.

If more data is needed, which will likely be the case with the intensive apps that will run in the car, customers can opt to select from a range of plans including $20 for 1 GB of data, $30 for 3 GB, or $50 for 5 GB.

GM is running the service through its OnStar service, which turns the car into a WiFi hotspot capable of connecting up to seven devices. OnStar customers will get a three-month free trial with LTE and then have the option to sign up for a new plan, with a $5 discount on the 200 MB or 1GB plan. Or, as further options, GM is also letting drivers buy day passes of 250 MB for $5 or a year's worth of data at 10 GB per month for $200 -- $150 if you're an OnStar customer.

The connectivity option will first be available on the 2015 Chevrolet Malibu, followed by more than 30 other Chevy, Buick, Cadillac, and GMC models before the end of the year.

Why this matters
In-car connectivity is still a relatively new market, and AT&T is emerging as the market leader in bringing LTE to the open road. Its business model has been a question mark, but it's clear the carrier is willing to experiment with all kinds of options to see what sticks. With Audi, it's offering data plans in six-month or 30-month increments, betting that customers don't want to deal with it every month. With GM, it looks as if anything goes. What consumers opt for, if anything, once a free trial is up, will be good learnings for the entire machine-to-machine communications market.

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— Sarah Reedy, Senior Editor, Light Reading