Is digital signatures impossible in the sense that on a live camera feed you can assign a signature to an object inside the feed and can for example track that object?

Example
Police helicopter camera in pursuit of a stolen car, there camera is manually controlled to follow the car and is relying on a person to find the car out of the other cars, is it not possible for the camera to assign some sort of signature to the stolen car (user defined) and then track that car with the camera, kinda like spray painting a big x on it.