Hi, I think its so good if you have car communication in your app. you can take the phone number of members, and make an icon for that number. This icon that show the veriety and color of car, can To be used as Identity of Owner of the car in the map. So everybody have an icon in the app and the others can have communication whit her, only by tap on her car icon. The members can show or hiden their number in the app.