We previously sold Lockitron units in the form you describe as a kit on Adafruit and Sparkfun. Send me an email I'll get you set up.
As for finding a secure NFC lock - I agree, it's slim pickings. The industry moved toward bluetooth in part because it lets you do random challenges defined by (your) software rather than (their) hardware.
As for finding a secure NFC lock - I agree, it's slim pickings. The industry moved toward bluetooth in part because it lets you do random challenges defined by (your) software rather than (their) hardware.