Recently I bought several NFC tags from ebay for my 820. I have been using the tags to trigger a location-based profile like turn off the Wifi when I leave home and turn on the WiFi when I reach home. I downloaded this app called EasyTag to write on the NFG tags. It has been working great and I found that enabling the tap&send function does not consume too much battery compared to enabling the 3G.
Just want to share this. I see tremendous application for the NFC features.