According to several web-sites the post iOS iPhone and 3G iPad are quietly recording the position of the device together with a time stamp into an internal hidden file.
This obviously makes it easy for anyone with the right access and software to extract the information and track your movements as far back as the data goes.
Although this is quite old news as it came out last year, many people are still unaware that iPhones can do this.
The researchers who found this, Alisdair Allan and Pete Warden, say that this capability must have been intentional by Apple the makers as the data is transferred to back-ips and is restorable. They have asked Apple to comment but have not as yet had a reply.
You can download an application HERE that will allow you to see what Latitude, Longitude and timing data the internal file "consolidated.db" holds.
The data it seems is not derived from Satnav but from telephone transmission mast geolocation (cell-tower triangulation).
It does not appear that the data ever leaves the device other than when backing up to a computer. But what Apples plans for this little data file remain unclear.
But a quick look at their iPhone software T&C shows that they've covered themselves legally.