Login to Android 6.0 with NFC card and Password I am evaluating MI5 and its NFC functionality. 
I am considering to compliment my Samsung Galaxy S4 GT-i9506 with MI5 because of various significant improvements in the hardware, software and sufficient expected userbase. 
I am trying to have two-step/three step security for the login of the phone by


NFC card (preferably dynamic) and Password
NFC card, finger print and password


There is a Security application in the new MI5 but I have not been able to profile it. I think it provides finger print and password authentication by default. 

I am going to replace the MIUI 7.0 OS with CyanogenMod 13 when sufficient experience of the device has been reached. 

NFC card

I would like to have a dynamic NFC card with time-dependent generation of authentications for the phone, like many bank systems work. 
However, I have not found such a card with battery yet. 
I think it should be possible with the dynamic NFC technology. 

YubiKey with smartphones motivated by Aleza's answer

I found this review about the product here in Amazon.com


  Love it for the desktop (I'm using it for LastPass and Gmail 2nd form
  authentication), but it sucks on mobile (which the a big reason I
  purchased it). The NFC range is terrible! I've tried everything
  (different positions, moving it, holding it still, restating the
  phone, toggling NFC on/off, restoring my phone's O/S, etc.) to get it
  to register but it only works 1-in-20 times. When I contacted YubiKey
  support then said to hold it closer... saying that because it's an
  unpowered device the range is very limited. But, I'm pressing and
  holding (20-30 seconds) it right against the back of the phone right
  where they said to hold it -- the only way to get closer would be to
  take the back of the phone off ;-(.
  
  I'm using a Samsung Galaxy 5, which they said they've had a lot of
  trouble with (though apparently the S6 is worse so be ware). I get
  that support from one phone to another can be iffy, but when 1/16" is
  out of range for a wireless connection, I would suggest there's a real
  design flaw.
  
  Disappointing...


I would like to get more pieces of information from the support about their sensitivity and reliability. They do not allow contacts from new customers; only from existing customers. I do not like such a philosophy; it does not confirm me. 

Thoughts about the product


Why is YubiKey's NFC weak in some products? 
Why you cannot get a replacement of weak YubiKeys? How are the warranty and return policies?
What is the company behind the product? 
Can the company recover the NFC key of the customer? 
Does the company maintain a database to whom they have sold those keys?




How can you use NFC card with password as login in Android >=6.0?
You can try YubiKey for an NFC card. It's not dynamic.
For NFC unlock + password, you can try SmartpassLock NFC.

Another (overkill) approach would be to use a contactless JavaCard (for example this one) that needs to have an applet in it, and infrastructure to support this kind of architecture. And then also develop an app on android for this(there are some smartcards apps, but havent tried them yet), the card uses a private and public key scheme.

Most apps, identifies the UID of the card to unlock, if you want something thats not off the shelf, a bit a coding will be needed.

Hope this helps!