Today's smartphones often have GPS, accelerometers, microphones, videocameras, and other information which could be used to determine what the caller is doing while they are calling you, and where they are.
It's nice to know that my friend is calling me from his cell phone, but is he relaxing in his
living room and genuinely interested in talking to me? Or is he just waiting for a traffic light to turn green and bored, and not really able to give me an attentive conversation. Am I on speakerphone or can I speak freely? Is the caller driving while he talks to me? What is the signal quality?
All these questions should be estimatable using the phone's recent GPS/accelerometer history as well as an ambient noise analysis. It would be nice to know that I won't be able to hear a word the other person says *before* I waste time picking up the phone.