Android NFC Reader Application

We require an application for android phones with build in nfc readers currently the nexus S but the app should suit other android hardware with nfc when further models are released. The application will require a md5 stored pin to use, this will be authenticated via our in house built web service, on successful authentication this will allow the user to scan an nfc tag serial number. that serial number together with the username/pass will be passed over the internet using https to our web service together with various other parameters such as timestamp, gps coordinate etc, where internet is temporary not available the app will cache the details and send at a later stage. In some cases the nfc tag will activate the display of information, this will be controlled by our backend system, the nfc app should simply react when it sees a certain flag from our web service Full details will be provided under nda