yes, whenever an app shows something shareable it should register onpeerready callback (note that we renamed this from onpeerfound). E.g., when the contacts app shows a specific contact, the gallery app shows one specific image, video app shows one specific video. In other cases the onpeerready should be removed. In the onpeerready callback you can either call sendNDEF (for short payloads such as a VCARD) or sendBlob that will trigger a BT transfer. Please take a look at the code sniplet on the wiki: https://wiki.mozilla.org/WebAPI/WebNFC#NDEF_P2P_Push_Example