Launching NFC when screen is Locked in Android

android nfc power-management

This is not supported. I don't think even Google Wallet works this way, are you sure about this? It is actually a security feature -- you don't want someone who stole your phone to be able to make payments with it without being able to unlock it.

android nfc power-management

According to Google, Android-powered devices must be unlocked in order to scan an NFC tag [1].Also the Google Wallet concerns privacy and security, and works only in unlocked state [2].

[1] http://developer.android.com/guide/topics/connectivity/nfc/nfc.html

[2] http://www.google.com/wallet/faq.html