I have an RFID tag that i use to access a building (3.2 GHz i think). I know i can program RFID tags with my galaxy nexus,but can i make my phone act as one (something like the google wallet nfc payment).
The card emulation mode is not available for the moment in the commercial releases of Android OS. The case of Google Wallet is special, because Google made this feature available only on for their application. There are other possibilities to emulate card, using SWP SIM-card secure element. This would mean that your phone should also support SWP cards. Or using Micro SD card secure element for card emulation, than you would need in the regular case also antenna extender.