In the Samsung Galaxy S3 Stock ROM NFC does not work when screen is off or locked. With this mod NFC also works when screen is locked or off.
There are two versions. The first just enables NFC, when screen is on, but it also worked when it is locked. Also with a PIN or Password-Lock everything is fine. But it disables NFC when the SGS3 is in standby and the screen is off.
The second version let NFC active all the time, even when the SGS3 is in standby and the screen is off.
Nothing else is changed in the behaviour of the NFC.
There are also two zips to go back to stock NFC, one is odexed and one deodexed. Use them only with the right firmware version (for example VPALEN).
All ZIPs have to be flashed with CWM. You should wipe Dalvik cache after flashing.
This mod works for at least for the firmware SPH-L710_VPALEN. This mod does not work with LFB now. I will provide an updated Mod in the middle of August because I am at vacation now.
Please give me feedback, because I do not own this device and I cannot test the Mod on it! I just ported my MOD for the international S3 to the L710.
Disclaimer: As always, I hereby absolve myself of responsibility for any damage you cause to your phone by flashing this. There is inherent risk in modding your device, and by flashing anything in this thread you are taking that risk into your own hands. If something goes wrong, I will try and help. You should always make a Nandroid Backup before flashing.
To ROM Devs: You are more than welcome to use this in your ROMs! Just shoot me a little bit of credit in your release post!
Thank you: Geniusdog254 for the idea and the infos in your thread.