This is using NFC, which is impossible to intercept. So only the person you send the key to can unlock and start your car with their phone, and you need to hack

This is using NFC, which is impossible to intercept. So only the person you send the key to can unlock and start your car with their phone, and you need to hack their phone to steal the key, which I believe is impossible given the way that Apple implements it (you need to steal their phone and know their passcode to use the key unless they set it in express, and even then the phone has to be unlocked within a certain time period to actually start the car).