Mobile app

I am running a new project for me and my company, and i need a simple Bluetooth device connected to a mobile app. For demo version, the mobile app should be based on google maps ( or other type) and it should allow login under 4 different type of users, User 1 ( red color), User 2(blue color), User 3(orange colo) and Regular User (green color)(they are automobile drivers). Every time the Users 1, 2 and 3 are putting an address to navigate to, the Regular User should be notified in proximity of 100 meters about the travel direction of User, 1,2, and 3. about he direction of where they are coming from, and where are going to, with an arrow both on device and mobile app. Ex: If one of User 1,2 or 3, i coming from behind Regular user, than he should be notify with alert and arrow about this. As a device and mobile app example you can check saphe.com The device is not ready yet, but the app should work without it, and it should be ready for use, when device will be ready. The device will only display the arrow with the direction and name of the user in proximity.
Just to be sure i have made myself clear, Lets supposed i am Regular user and driving my car normally on the road. If User 1 for example, is passing behind me and is coming in the proximity of 100m, than i should be notify with an arrow pointing up, that he is behind me traveling same direction with me. If he is planing to turn left, than i should see this. The way you can predict where this User is going to, is because they will put on the navigation a certain destination, and based on that destination, you can predict when in 100 proximity, the direction of movement. Note that the final destination of Users should be hidden from other users.
I need it only for android for the beginning.