Many smartphones have accelerometers inside. I’m sure some app developer could make an app that would detect when you’re driving and program it to detect that sudden deceleration/stop/crash and dial 9-1-1. My phone rides shotgun in airplane mode. It wouldn’t be much use.
My dashcam app (Hovans Autoguard?) will do that. If it senses an impact, it will archive the video clip. But, there's the previously mentioned problem of survivability after an accident.