Do you have some code to read MECARDs or a spec sheet?

I don't know if the current 2D decoder handles vCards (it used to, not sure if we re-implemented it in the new plugin).

Re exporting contacts, what do you mean by this? The Contacts app can export contacts - or do you want to be able to read a QR code containing a contact and then give the option to either save the file and/or import it into the Contacts app?