I'm currently trying to detect when a car is parked via Android. I was thinking of using the Android Detected Activities (https://developers.google.com/android/reference/com/google/android/gms/location/DetectedActivity) and detect a switch between IN_VEHICLE and ON_FOOT. But it means polling the device regularly so it's not really power efficient.
Do you think it's reliable enough ? Also, maybe there is a better solution ? What do you think ? I also think about using Bluetooth and detect when the car's bluetooth is unpaired but everybody doesn't use Bluetooth.