You can use your phone to check your calendar, contacts, music, email and more – just don't try using it to make calls.

That's the rule for drivers without hands-free devices in an increasing number of states – including California, starting next week.

Beginning July 1, adult California drivers talking on their mobile phones without a hands-free device are subject to a $20 fine and a run-in with the law. The Golden State's new traffic ordinance follows similar versions adopted in Connecticut, New Jersey, Washington state, the District of Columbia, New York and the Virgin Islands.

While the fines aren't wallet-busting, there's a hitch. Except in Washington state, an officer can pull you over solely for talking on the phone without a headset.

The laws are even stricter for new drivers. As many as 17 states and the District of Columbia ban cellphone use entirely for minors and new motorists while operating a vehicle (see map). They include California, Colorado, Connecticut, Delaware, Illinois, Maine, Maryland, Minnesota, Nebraska, New Jersey, North Carolina, Oregon, Rhode Island, Tennessee, Texas, Virginia and West Virginia.

The states' cellphone driving laws were adopted with safety in mind. Studies by the Harvard Center for Risk Analysis (.pdf) suggest 2,600 people are killed and as many as 330,000 people are injured each year in the United States in cellphone-related driving accidents.

"According to some estimates, getting drivers' hands off the cellphones and onto the steering wheel will save almost 300 lives a year in California," Gov. Arnold Schwarzenegger said at a recent news conference.

However, hands-free devices may not help. Researchers at Carnegie Mellon University have noted that voice-activated or hands-free calling is a major distraction, too.

Also, while talking may be banned, text messaging generally isn't. Only Washington, Minnesota and New Jersey ban texting outright. That means in California, for example, a motorist can legally fumble around with a handset sending a text message, but will be breaking the law if he holds the phone up to his ear and starts talking.

Electronic stores, mobile-phone shops and online retailers are taking advantage of the new law to offer a wide range of specials on hands-free headsets. Headsets.com, for example, is offering a free (wired) headset to anyone who sends them a copy of a traffic citation for making calls while driving.

And be sure to check out Wired.com's roundup of wireless headsets for our recommendations on the best hands-free gear for your phone.