By Brendan Benzing

You just left the house, and realized you forgot your wallet. Do you go back?

It depends. Sure, you could borrow money or go without lunch today. You may even risk getting pulled over without your driver's license.

But what if you forgot your mobile phone? Would you go back then?

For many, this has become an even harder decision. You could borrow a phone, but none of the people you call will answer, because they screen calls.

But would it matter, because you probably don't even know the phone numbers of frequently-called friends anyway?

In addition, the people who want to reach you on-the-go won't be able to get in touch either. And if you are like most consumers, you are not just making calls on your phone -- you are also sending emails, text messages, IMs and social network updates.

The mobile phone has become your unified communication device, 24/7.

The two items that people say they would return home to collect after realizing they forgot them are the mobile phone and the wallet. I would put my money on the mobile phone to surpass the wallet.

The old American Express tag line of "Don't leave home without it" may soon be more applicable to the mobile phone than the iconic AT&T campaign of "Reach out and touch someone," which exemplifies the emotional connection of telecommunications.

In most countries, you cannot buy lunch with a mobile phone. But consumers can make purchases using their phones.

For marketers, this trend is important to watch.

Think back to the middle of this decade when abandoned shopping carts were the challenge of every emerging online retailer.

It certainly took some time to get consumers comfortable with the entire online process. But now that their credit card numbers are on file with so many retailers, all they really need to do is sign in, authenticate and purchase.

Today, there are new services that enable you to pay with "cash" via your mobile phone. Near Field Communication (NFC), a technology that enables consumers to merely wave their phones in front of a reader, is emerging as a go-to payment method.

While it still may be a few years before that is commonplace, there are trials going on in Malaysia, Britain and other countries that are proving promising.

In fact, Reuters reports that 50 percent of consumers in Japan have mobile phones that replace the need for a wallet.

For the mobile marketer, now is the time to begin building relationships with its customer through their mobile devices. This certainly is a delicate process given the personal relationship individuals have with their devices.

The mobile device is truly the converged experience that has been promised for over a decade.

In terms of retail, the mobile phone will support transactions and enable consumers to gather product information from retailers, as well as provide a 24/7 customer feedback loop and connection.

Very soon, cashiers around the globe may be asking consumers, "Cash, credit or mobile phone?"

Brendan Benzing is vice president of new product strategy and marketing at Motricity, Bellevue, WA. Reach him at .