It's often said that the average person will never leave the house in the morning without three things: their mobile phone, their wallet, and their keys. If three of the top mobile operators in the United States have their way, this summer people will begin to seriously consider leaving one of those behind.

So long, wallet? That's right, this summer may be remembered as the beginning of the era of mobile payments, services that let consumers pay for things in-person through their smartphone rather than with cash or a credit card. Isis, a joint venture between AT&T, Verizon Wireless, and T-Mobile USA, is the mobile operators' answer to Google Wallet, a similar service launched by Google last year. Dozens of brick-and-mortar shops (many nationwide chains) have already begun to accept such payments. Google Wallet currently counts more than 25 big brand chains as partners: Gap, Macy's, Toys R Us, Office Max, RadioShack, Sports Authority, Foot Locker, among them.

More relevant for this publication's readers, however, are the restaurants, coffeeshops, and convenience stores that have signed up. Peet's Coffee & Tea, Jamba Juice, Jack In the Box, Einstein Bros. Bagels, Walgreens, CVS, and more are onboard.

Once our wallets become "smart", our eating habits could get smarter, too. While there are plenty of privacy and security issues to unravel first, it's not too big of a leap to imagine health apps in the near future that help people on diets. Trying to stick to a low carb diet? Maybe your health app won't allow purchases at the bagel shop. Figured out that late night eating is your biggest vice? A smart wallet could put the brakes on spending after 10 PM. Drinking too many sugary coffees each month? A health-conscious mobile payments app could enforce a monthly Starbucks budget.

While such rules may not be the keys for success for everyone -- for some, the implications for health behavior change could be huge.

Walter Frick over at BostInno has a worthwhile post on the potential "good behavior" layer that the coming mobile payments era might enable. If successful, mobilizing payments could change many more behaviors than those that impact a user's health.

Few would be as important, though.