NEW YORK - Major chain stores are testing a tracking system through shoppers' cellphones to monitor their shopping habits.

The system picks up WiFi signals and phone IDs to determine how often consumers visit stores and even sections within stores. Then, companies use the information to send emails and coupons or to learn better ways to advertise products.

Lawmakers say they don't like that shoppers don't know which stores are tracking them.

In a news conference, Sen. Charles Schumer said the tracking is too invasive. He says he has written a letter to the Federal Trade Commission, asking the agency to require retailers to allow customers to opt out of being tracked. He says he also wants the FTC to mandate that stores indicate that they have the tracking system.

Schumer's letter will now make its rounds in the Senate to get signatures of support.

Customers who don't wish to be tracked can turn off their WiFi or leave their phones at home.