Cellphones increasingly contain everything needed for financial transactions. A Google Wallet demonstration in New York. Shannon Stapleton / Reuters

In London, travelers can buy train tickets with their phones - and hold up the phones for the conductor to see. And in Starbucks coffee shops in the United States, customers can wave their phones in front of the cash register and pay for their soy chai lattes.

Money is not what it used to be, thanks to the Internet. And the pocketbook may soon be destined for the dustbin of history - at least if some technology companies get their way.

The cellphone increasingly contains the essentials of what we need to make transactions. "Identification, payment and personal items," as Hal Varian, the chief economist at Google, pointed out in a new survey conducted by the Pew Research Center in Washington, D.C. "All this will easily fit in your mobile device and will inevitably do so."

The phone holds and records plenty more vital information: It keeps track of where you are, what you like and who your peers are. That data can all be leveraged to sell you things you never knew you needed.

The survey, released last month by the Pew Research Center's Internet and American Life Project along with Elon University's Imagining the Internet Center in North Carolina, asked just over 1,000 technologists and social scientists to opine on the future of the wallet in 2020. Nearly two-thirds agreed that "cash and credit cards will have mostly disappeared" and been replaced with "smart" devices able to carry out a transaction. But a third of the survey respondents countered that consumers would fear for the security of transactions over a mobile device and worry about surrendering so much data about their purchasing habits.

Sometimes, those with fewer options are the ones to embrace change the fastest. In Kenya, a service called M-Pesa (pesa is money in Swahili) acts like a banking system for those who may not have a bank account. With a rudimentary cellphone, M-Pesa users can send and receive money through a network of money agents, including cellphone shops. And in India, several phone carriers allow their customers to pay utility bills and transfer small amounts of money over their cellphones.

Several technology companies, big and small, are busy trying to make it easier for us to buy and sell all kinds of things without our wallets. A start-up, WePay, describes itself as a service that allows the smallest merchant - say, a dog walker - to get paid; the company verifies the reputations of payers and sellers by analyzing, among other things, their Facebook accounts.

A British start-up, called Blockchain, offers a free iPhone application allowing customers to use a crypto-currency called bitcoins, which users can mint on their computers.

A company called Square began by offering a small accessory to enable food cart vendors and other small merchants to accept credit cards on phones and iPads. Square's latest invention allows customers to register an account with Square merchants and pay simply by saying their names. The customer's picture pops up on the merchant's iPad.

Google Wallet has been designed to sit in your phone, be linked to your credit card, and let you pay by tapping your phone on a reader, using what is known as near field technology. But Google Wallet works on only four kinds of phones, and not many merchants are equipped for near field technology.

Meanwhile, PayPal, which allows people to make payments over the Internet, has quietly begun to persuade its users to turn to their cellphones. PayPal posted about $118 billion in total transactions last year and became the fastest-growing segment of eBay, its parent company.

"The physical wallet, which had no innovation in the last 50 years, will become an artifact," John J. Donahoe, the chief executive of eBay, told me recently. The wallet would move into the cloud, and ideally, from his perspective, into PayPal. No more would the consumer worry about losing a wallet. Everything, he declared, would be contained within PayPal. It would also enable the company to collect vast amounts of data about customer habits, purchases and budgets.

Mr. Donahoe said he wanted his company to become "a mall in your pocket."

I recently described PayPal's plans to Alessandro Acquisti, an economist who studies digital privacy at Carnegie Mellon University in Pittsburgh. Mr. Acquisti smiled. If today all you need to do is enter your phone number and PIN when you visit a store, perhaps tomorrow, he said, that store will be able to detect your phone by its unique identifier. Perhaps, you won't have to shop at all. Your shopping data would be instead collected, analyzed and used to tell you exactly what you need: a motorcycle from Ducati or purple rain boots in the next size for your growing child. Money will be seamlessly taken from your account. A delivery will arrive at your doorstep. "In the future, maybe you won't have to pay," Mr. Acquisti offered, only half in jest. "The transaction will be made for you."

The New York Times