Hi @yeka,
Imagination is the limit I guess. 
You can integrate easily with IoT devices and much more via IFTTT in more secure and painless way then programming you own locks, doors etc. (just an opinion).
My example for Vivokey Spark 2 auth, with IFTTT behind is in this thread:
So, whatever you can program your server side to do, NFC client can just fetch and stay light.
Cheers,
V