If I understand correctly, what you want to do is
- User scan card on the reader(the card logger a.k.a Arduino)
- After 30min, smartphone reads the data in the logger?
- Sync the read data with a database
If so,
In (1), you can use NFC connected to Arduino to read the cards then, you can use bluetooth to transfer the data read, from the logger(Arduino) to a smartphone which completes point (2). I don't know about point (3) though.
Do you really need to read the data in the logger(Arduino) from a smartphone? If you can use a laptop, then there's no need of a bluetooth since Arduino can communicate with laptop through serial communication.