Fitbit CEO James Park shows off one of his devices as he poses for photos outside the New York Stock Exchange, before his company's IPO, Thursday, June 18, 2015. Fitbit makes devices that can be worn on the wrist or clipped to clothing to monitor daily steps, calories burned and grab other data. (AP Photo/Richard Drew)

Fitbit accuracy questioned in lawsuit

The class-action lawsuit, filed earlier this year, argues that the PurePulse technology used in the Fitbit trackers that measure your heart …