For now, GOFAR works with 1 device per car. If your phone is not in the car when your partner drives, the ray still works, and the trip will be uploaded to your phone the next time you are in the car. The only thing you will miss out on will be the map of the trip in trip details, as GOFAR uses the paired phone to provide the GPS data. We are working on allowing multiple accounts to connect to the same device. We will let you know as soon as this is ready.