AT&T shared data plans launch late August, start at $45 per smartphone

The cost per gigabyte and smartphone decreases as customers add more data to their plan, so 4 gigabytes of data has a base price of $70, plus $40 per smartphone, all the way up to $200 for 20 gigabytes of data per month and $30 per smartphone.

Cellular capable tablet-style devices like Apple's iPad are less expensive, and will cost $10 per month to add to a shared data plan. Laptops and mobile hotspot devices are another $20 each month, while basic and messaging phones can get shared data, unlimited talk and text for $30 each month.

The new shared data plans allow customers to choose open of AT&T's existing individual or family plans, and current customers are not required to switch to the new plans. Those who decide to switch to AT&T's shared data plans can do so without a contract extension, and the rates are also available for business customers.

Customers can choose up to 10 devices to attach to their shared plan, and at least one of those devices must be a smartphone. The plans include tethering and unlimited domestic calls and texts for smartphones.

"We offer customers a broad choice and the best lineup of plans, now enhanced by Mobile Share," said David Christopher, chief marketing officer, AT&T Mobility. "With these new plans, the more you share, the more you save. They’ll be a good fit for a variety of new and existing customers. But if customers want to stay on their current plan or choose from our existing plans, they can do that, too. It’s their choice."

AT&T's press release states that the new mobile share plans "give customers more control over how, where and on what device they use data." Customers can choose to use more of their data bucket on their tablet, or tap into it only when needed for devices that might be used only occasionally.

"Today we think of people’s smartphones and tablets sharing a bucket of data. But in the future we’ll see health care monitors, connected cars, security systems and other devices in the home all connected to the mobile Internet," Christopher said. "Our Mobile Share plans are simple, easy and a great value for individuals or families with multiple mobile Internet devices."

Competing U.S. carrier Verizon launched its own shared data plans on June 28, called "Share Everything." With it, line access for smartphones like Apple's iPhone run $40 per month, while tablets like the iPad are $10 per month.