Imagine walking up to a soft-drink machine and having your appearance analyzed. A young woman, for example, could then see advertising for Diet Coke or bottled water.

A man walking up a minute later would have a totally different experience.

• Find an online broker and start trading

That kind of technology is being used in Japan, where vending machines at train stations and other locations tweak their wares to fit a person's gender and age, The Wall Street Journal reports. "The idea is to transform billboards and the like into sophisticated marketing tools that identify and target a specific audience."

The displays, made by NEC Corp. (NIPNF), use facial-recognition technology to learn more about the people using vending machines. NEC says the systems are 90% accurate in determining someone's gender and 70% accurate in guessing within 10 years of a person's age, the Journal reported. Post continues after video:

Those systems may raise privacy alarm bells in the U.S., but in Japan they're perfectly legal. NEC says the systems don't store pictures, and the company recommends posting a warning near them alerting people to what's going on.

I'm surprised more systems like this aren't in place. Delivering specialized advertising to shoppers at the mall, for example, would seem extremely valuable to companies. Imagine looking at a mall directory and a nearby screen starts advertising sales at stores you were actually interested in.

Mobile applications have long been considered the next frontier in targeted advertising. Smart Spending reports that one app, called Shopkick, gives iPhone users rewards when they stop in certain stores, and can offer even more rewards for trying on clothes.

More from MSN Money:

• Do-Not-Track the new Do-Not Call?
• Help! I'm being stalked by a diet ad
• Coupons that find you