Here is a video of ObstaNex, by NEXYAD, detecting cars with a regular smartphone, feeding the real time Driving risk computing SafetyNex with additional inputs such as Interdistance, for instance.
ENHANCED safety functionality for everyone (every smartphone or modern dashcam owner). Detection results may vary a little depending on quality of camera, but anyway, it brings safety alerts and can save your life.
Already integrated into dashcams for intelligent telematics.