AT&T also plans to add a feature in the fourth quarter that might simplify how the business use of mobile is paid for: It will allow users to put one device on two different plans, one for personal use and one for business. Enterprises will be able to assign all activity carried out by the "work persona" of the device onto a corporate rate plan, Hill said.

"As we move away from the unlimited plans, employees are not going to want to come into the enterprise and .... do corporate work on their own dime," Hill said.

The feature could effectively allow enterprises to recreate the traditional employer-paid mobile account without having to buy and manage devices or worry about personal versus business use.

AT&T can only actually do that account-splitting for its own subscribers, but it's working on ways to let other carriers do the same thing for Toggle users. Toggle's dual device personalities already work on devices from any carrier. To make split plans possible, AT&T is studying how it might share usage data for the corporate portion of a phone with other service providers, Hill said. It already delivers that information to its enterprise customers. Other carriers could use the same data to put together a bill for their subscribers.

Toggle can be useful beyond the classic corporate office environment, Hill said. For example, grade schools could build special profiles for each grade level, with different materials and assignments, and have the right profile pop up on a shared tablet when a student from that grade logged into it. For workers in the field who share a company vehicle, each could customize a device to his or her own preferences and needs and get those by logging in, Hill said.