Hi, Just saw this post while looking at NFC applications.
I see what you want to do (Grab an identifier from the phone to validate phone/user identity and trigger an action)... perhaps there is another way to do this.
Use NFC, but have the smartphone's user enter an identifier to authenticate.
It's not complicated to add the NFC interface (and BLE if you want) to any Arduino board with this module (tutorial on Github). The TapNLink PRIMER NB can be configured with a login and password for access control.
The difference is that you would tap once to establish the NFC connection and launch the app on the smartphone. Enter the login/pasword. Tap a second time to trasfer the login and password to the module.
You could also use the NFC and BLE together... tap one to launch the app and pair the Bluetooth LE connection. Then log in while connected by Bluetooth.
I know it's not exactly what you set out to do... but it may be easier at get you the access control that your want.
I am interested in knowing if you work out another solution. Always interested in seeing NFC used.