No need to check-in using Foursquare, Gowalla, or Facebook. The Guardian reports of a secret file on iPhones that records your movements and has been doing so for nearly a year!

The hidden file contains the latitude and longitude of the phone’s coordinates along with a timestamp. Security researches believe that up to a year’s worth of data may be stored on your iPhone. The movement tracking seems to have been introduced shortly after iOS 4′s release in June 2010.

“Apple has made it possible for almost anybody – a jealous spouse, a private detective – with access to your phone or computer to get detailed information about where you’ve been,” said Pete Warden, one of the researchers.

Below is a visualization of an iPhone user’s movements across the southwest of England.

Simon Davies, director of the pressure group Privacy International, said: “This is a worrying discovery. Location is one of the most sensitive elements in anyone’s life – just think where people go in the evening. The existence of that data creates a real threat to privacy. The absence of notice to users or any control option can only stem from an ignorance about privacy at the design stage.”

Is this Apple not taking privacy seriously or could it be the starting point for some location based service coming in future iOS releases?