Programming is a community. It would be stupid to be a pioneer and to do everything from scratch. Someone someday must have faced the same problem you are facing and found a solution for that problem. It's either patented or given back to the programming community.
We were lucky (and maybe smart?) to search for an API that tracks users movements.
We found Google Awareness API a scary though very useful solution.
Google API is a Android supported API that statistically guesses what the user is doing at any given time.
These are it's indicators:
Time - Current local time
Location - Latitude and longitude
Place - including place type
Activity - Detected user activity (walking, running, biking)
Beacons - Nearby beacons matching the specified namespace
Headphones - Are headphones plugged in?
Weather - Current weather conditions
We decided to focus our app which focuses on finding the right time for a phone call on when the user is walking or driving. A major breakthrough in terms of developing the