Another challenge is that ADP faces a wide spectrum of competitors, including nimble startups like Workday -- the company started by former PeopleSoft CEO Dave Duffield -- as well as established players like Ceridian.

ADP thinks it can do well because of the range of services it offers, which continues to expand. In recently bought AdvancedMD, which will give it a footing in practice management services for doctors, and last July it bought Workscape, which sells a high-end benefits administration platform.

But Capone acknowledged that some of ADP's services need better interfaces, hence the update planned for October. "People expect a better experience these days. They expect to get the Web 2.0-Facebook type experience when they come to work," he said.

The mobile applications are also a step in that direction. The payroll app will let employees scroll through pay statements and view data such as gross salary and taxes paid to date, as well as manage benefits and other tasks from a smartphone.

They'll be good for employers, Capone argued, because they'll let workers perform tasks themselves, without having to bother the HR department. And they'll be secure, he said, because no data is stored on the device. "Nothing resides on the phone, everything is in our data center," he said.