The photos -- one said to be from July and one snapped last week -- created a stir on blogs, chat rooms and Twitter after they were posted online.
Retribution for the violation seemed to be coming from no less than the state's top elected official: her husband.
On his Twitter feed Tuesday afternoon, Schwarzenegger wrote to TMZ.com founder Harvey Levin: "Thanks for bringing her violations to my attention. There's going to be swift action."
Hours later, the Web site added a video it says was shot Tuesday in Brentwood, Calif., where the family lives. It briefly shows Shriver behind the wheel of a large black SUV and holding a cell phone to her ear. She then appears to put the phone down as she drives past the camera.
On Wednesday Shriver released a statement apologizing for the behavior and saying that she will donate the old cell phone seen in the photographs to charity.
"That's my version of swift action with a higher purpose," Shriver said.
Earlier Schwarzenegger spokesman Aaron McLear explained earlier that by "swift action," the governor means he'll ask his wife not to hold the phone while driving, but there could be monetary consequences as well.
Schwarzenegger signed a law last year requiring California drivers to use a hands-free device when talking on cell phones. Since then, the California Highway Patrol has issued more than 150,000 citations, according to The Associated Press. That figure does not include citations issued by local police.
State fines for driving while using a hand-held device are $20 for the first ticket and $50 for subsequent tickets, plus additional fees.
In Los Angeles County, where Brentwood is located, the fines are $93 for the first ticket and $201 for the next one, meaning Shriver could have owed at least $300 in fines and court fees had she been caught by police.
The Associated Press contributed to this story.