07-29-2014 02:51 PM
I'm not sure what you mean here. Headless applications can use the instant preview, which a user can click on to open the UI of an application. Does that answer your question? More details can be found here: Headless applications
08-15-2014 05:42 AM
Just to add to Mark's response I'd be interested to know what use-case you have in mind that you believe would require you to have access to an NFC tag from a headless application.
The nature of NFC as a close range radio link constrains use-cases to ones where the end-user has to take some physical action to "tap" the handset onto an NFC tag, an NFC reader or even another NFC device. NFC use cases generally require some element of interaction with an application via the UI -- for example, it would be unacceptable and illegal to allow a background application to approve a contactless credit card purchase without an auditable approval from the user. It's for this reason that NFC apis, and in fact the radio, are generally fully accessible only when an application is in the foreground. NFC is also tightly integrated with the Invocation Framework which allows the OS to launch the appropriate app into the foreground on the detection of a suitable NFC event so the need to use a headless app isn't necessary.