It's just a simple nfc tag, but manufactured in a bio-compatible form like a pet tag. 

You can write whatever data you want to them, be it access control credentials, vCards, urls, text...

In this case I was using LNurlW to create a LN faucet so people could receive sats just by tapping their phone to my hand. 

 Yes, I know. But how did you put it in? That's what I want to know.  

 Well, that was interesting 🤣
nostr:nevent1qqsx35cv8ggmazc795pqzdzllnc7qr7hjhzt2npj8cxyr3qvknc7encpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsyg9gplz20p35acn2409vj5d5eltm26hp3w4ax0z6lh8khmtdeq8t6ypsgqqqqqqs30l5rh 

 It's a weird way to pay for cookers and blow 🤣🤣🤣