It is no secret online retailers have been gathering information on consumers for some time, but it turns out brick-and-mortar retailers are, too.

The purpose is to enhance the customers' experience by tracking their movements to gain a better understanding about what each person likes or dislikes and what they are ultimately more likely to buy.

Retailers are doing this by using Bluetooth boxes, which work to gather data by communicating with a consumer's mobile device. For the Bluetooth device to communicate with the phone, the customer has to have the store’s app or at least a special code that allows the devices to talk, Real Estate Tech News reports.

A number of malls use a similar technique but offer free WiFi to achieve this. When consumers agree to the terms and conditions to connect to the WiFi, many shoppers are also agreeing to have their data tracked while they are on the premises.

Some retailers are going even further by using an accelerometer — a sensor built into a phone that can measure movement, according to RETN. An accelerometer will tell retailers when shoppers are walking in their direction or if they are visiting a competitor. In some cases, it can even track shoppers all the way to the parking lot if their GPS is turned on.