GeoPost

This app can be used to track people, fleets and Assets. They need to carry the mobile with them. User has to grant GPS Location permission to send location updates to server .
View Fleets display all fleets on map. Enter the mobile number and click View to see specific fleets. Empty mobile number and click on View displays all fleets.

Link to view fleets on google map
http://www.kottapa.com/Fleets/AllFleets.html
Click on the available markers to see more details

The app can be customised as per the requirements.
Customisation includes

Update interval
Accuracy of the location to save battery
Info displayed on map
Filter the fleets that should visible on your map

and any other changes needed by the customer.

Test steps
Install the app
Enter your phone number
Press "Start Location Updates" button
Wait for few seconds.
The top label "last upd" will display last location updated time.

Check your location using "View Fleets" button. Click on the available marker to get details and click on call icon to call the user
Stop location using "Stop Location Updates" button