Nightly News | December 15, 2013
>>> for those of you who haven't started your christmas shopping yet, there are just nine shopping days left. we have a warning for bargain hunters . the apps you use to find the best deals are also being used to find out a bit more about you.
>> reporter: chicago and maureen brown is hitting the stores this holiday season .
>> let's see.
>> reporter: smartphone in hand.
>> i have the best buy app, target, cvs, wall green's. they send you coupons and let you know what kind of deals they're offering.
>> reporter: at sears it is part social network .
>> there are people who checked in and give tips.
>> they give tips. they can post surveys, you can say which of these shirts is more fashionable.
>> reporter: this year more shoppers than ever say they'll use smartphones to use more about stores but at the same time, stores are using our phones to learn more about us. apps like shop kick already alert 6 million users to deal when's they walk into more than 7,000 stores. like best buy , target, jcpenney. very soon if you let them, they'll foul as you shop at select macy's.
>> we can send customers notifications about products they love as they're standing right near that product.
>> reporter: the analysis firm retail next can follow a smartphone's wi-fi signal to follow traffic, even seeing how many people walk past the door.
>> we can get those numbers and we can understand. wait a minute. what do i need to do differently to get more customers to come into the store?
>> reporter: if that feels too much like big brother , shoppers can disable their wi-fi.
>> a consumer that knows exactly what they want out of an application and exactly what he or she is willing to give up in materials of privacy or other information can get a lot out of these applications.
>> reporter: for maureen brown , sharing her name, e-mail address and shopping habits is part of the deal.
>> we put so much information out there blindly.
>> to lots of people we're part of the problem.
>> reporter: for now she's willing to give up some privacy to save some money. nbc news, chicago.