Unfortunately GPS nor cell phone work in all locations.  Tough in the city with buildings blocking signal and in woods with heavy foliage.  Most elderly people don't have computers to track and this would be confusing for them.  This may be fine for a person in the very early stages of Alzheimer's, but where this would truly be needed is the person in the wandering stages that truly don't know how to come back home and chances are they would not have the device with them to track them anyway.  Alzheimer's individuals don't know how to use the necklace or bracelet to ask for help if they have fallen with devices such as "lifeline" and other devices.