How secure outdoor?
I wonder how safe the scheme is outdoor. It is 100% certain that the user has both the PC/tablet and the phone in/around their body or bags. Can we expect a knowledgeable thieve to forget the phone when he can steal the PC/tablet?
This scheme is indeed a 2-factor authentication when the user stays indoor but it is 1.5-factor authentication at best when they move around outdoor. People should be advised to remember the secure enough password/PIN without depending too much on the possession of a phone.