that may not be ideal. most people keep their sms history, so the person trying to use the service in my behalf could just scroll the screen. or do you mean some sort of one timer passcode? that could complicate things a bit, not sure how it could work
You could call them and enter a few numbers I guess. This isn't stored, at least on my phone since you are in a call, and can be automated. ( Or just don't store that message. )
