Shoes with an in-built tracking device to locate Alzheimer's patients have gone on sale in the UK.Designed to give worried relatives and friends piece of mind, the shoes enable the persons with Alzheimer's to be monitored remotely, giving them more freedom. One of the most common concerns for families of an Alzheimer's sufferer is that the person often becomes lost after getting confused and disoriented. The 250 shoes are fitted with a miniature GPS system - similar to those used in sat-nav systems found in cars - that allows its wearer's location to be accurately pinpointed. Relatives are even able to set up a designated 'safe' area so if the person strays beyond those boundaries, it would trigger an alert in the form of an email or text message.  Family members use an app downloaded to a smart phone or computer to find out the location of the missing person. The GPS system is implanted in the heel of what appears to be a normal walking shoe. The device, which cannot be seen or felt, contains a battery, SIM card (this is what tracks the wearer) and an integrated chip to help the device function. The antenna and a USB connection to charge the shoes runs up the back heel of the shoe. The shoes need charging roughly every two days, a process that takes roughly two hours.