Panasonic's P506iC makes a tinkle noise when it pays for coffee

The Felica system lets those with compatible mobile handsets get cash and carry out other secure credit card-based transactions using a 3G network.

A credit card-sized Sony smart card powers the system. It holds a chip which can be loaded with personal data.

The handsets have built-in security to stop others using the service.

Fingertip cash

With a subscription, the wallet phones work by sending data at high speeds and securely over the DoCoMo network.

Special readers can also be built into cash machines and cash registers to recognise the transactions.

DoCoMo is the world's biggest mobile network

One of the first 3G handsets which runs the service is Fujitsu's F900iC.

Other compatible mobiles include those by NEC, Panasonic, Sharp, Mitsubishi and Sony Ericsson.

As well as all the usual functions a 3G phone has, the handsets can be password-protected, and the F900ic can also be locked and access with through a fingerprint scanner.