NTT DoCoMo, Japan's largest mobile phone operator, hopes to one day sell a handset that lets you make electronic payments while it stays in your pocket.

Using mobile phones to pay for goods electronically is common in Japan, the world's biggest market of third-generation (3G) mobile users, where phones are swiped at ticket gates or vending machines to pay for train fares or drinks.

DoComo's prototype cellphone, unveiled on Tuesday, would allow you to do all that without taking it out of your pocket.

The phone, which uses a sensor made by start-up Kaiser Technology, sends electric signals through the human body to transmit data, enabling electronic payments or data transfer at the touch of a finger.

It is the first to pack a type of near-field communications technology, researched by IBM and used by Matsushita Electric Works in ID tags, into a handset.

Doors to secure areas would open as your phone transmits your ID code through your feet, or you can get in a car and have the car instantly adjust the seat and steering wheel to the perfect angle, said DoCoMo spokesman Takushi Koinumaru.

But it will take several years before the new touch-sensitive handsets are ready, reliable and safe for Japan's nearly 9 trillion yen ($77.81 billion) mobile market, if ever.

"We don't know yet if we can commercialize this technology," Mr. Koinumaru said. "We need to conduct more research. Then we need to see if there actually is a market for this."