SMS and iMessage are exposed via Bluetooth’s Message Access Profile. Facetime would use the Hands Free Profile. Access to both of those would be requested during pairing of the phone.
At least on iOS, the other apps would need permission to integrate with the necessary API to integrate with MAP. I’m not sure if this is even available with the public APIs.
At least on iOS, the other apps would need permission to integrate with the necessary API to integrate with MAP. I’m not sure if this is even available with the public APIs.