This type of 'layering' could be done with other devices in the eco-system, too. The Apple Watch for (a crude) example:
> Does this person have an Apple Watch? Is the device in range? Is it unlocked? Do the wearer's biometrics match?
Most individuals have (for better or worse) bought into the (relatively) closed system of Apple products – why not continue leveraging that to their advantage?
I worked on a very similar project a few years back, but without lookup and with an altogether different (physical) interface: http://iamsaul.co.uk/projects/message-box/