Primarily because tracking people 24/7 through GPS in their phone is a privacy no-no. Next tot that: GPS is really unreliable in buildings and oldfolks tend to live in appartment blocks. Also hight (floor) is an issue as well as battery life.
Also, why would this be a no-no? How do you think map applications work? And 'local recommendations' apps?
EDIT: Add link to Apple / Google tracking GPS on phones http://abcnews.go.com/Technology/google-apple-track-users-lo...
I think you may believe I want the patient to carry the phone, but I am suggesting the nurse.
My father worked in Public health for 40 years, two decades ago we explored the idea of cards such as this for patients, but came to the conclusion they fell short for a variety of reasons, including patients losing the devices, patients transferring to different clinics and not having their original card etc etc. As is the case with current medical records, there is a stronger guarantee the doctors will be able to review existing case history is the data and files are stored with the hospital or care provider, not receiver.
Finally, I am pretty sure the nurse can charge a phone daily.