"The great advantage of voice is that all computers and phones have the sensor built in, whereas other biometrics require additional sensors," says Mike Brookes, a signal-processing researcher at the Imperial College of Science, Technology, and Medicine in London, who specializes in voice recognition. And, he adds, voice recognition also allows you to keep your hands free.

"Voice has been on the verge of breaking through for a number of years," says Brookes. He believes voice verification technology will finally start to take off, particularly with telecommunication and cell-phone companies, who are keen to push e-commerce services via Internet-enabled cell phones.

Another reason for the adoption of voiceprinting is the recent introduction of so-called "smart" credit and debit cards. These cards have eliminated the use of handwritten signatures for authenticating payments, and instead require customers to punch in a four-digit PIN, which is then verified against a number stored on a chip on the card.

Since the recent mass introduction of these PIN-verified cards in the U.K., for example, most types of credit-card fraud have plummeted. According to figures released in February by the U.K.'s Association for Payment Clearing Services (APACS), credit-card fraud dropped by 13 percent in 2005.

But one type of fraud continued to rise last year, by 21 percent: the problem lies in transactions made over the Internet, by phone, or by mail order. In these kinds of transactions, a card's information can be read out or typed in without additional authentication. The field of biometrics, in general, and voiceprinting, in particular, could go a long way toward solving this problem, Harris says.