The reason why they use phone in the first place is that you will always have it with you. The reason why you have your phone with you is because you use it to

The reason why they use phone in the first place is that you will always have it with you. The reason why you have your phone with you is because you use it to make phone call. Unless you are suggesting to buy phone that supports dual SIM cards, I think this idea is not very practical. Why not have physical TFA device instead (they are usually much cheaper and lighter than a phone)?