Psst. Folks in Aus. The Telstra plastic pit covers? Newish ones? They have a little NFC icon in the corner.
You’d better believe that’s an NDEF-formatted [correction: unformatted but NDEF-capable] NFC card chip embedded in the plastic.

And oh yeah, it’s writeable.

New dead drop system invented — NFC shoes picking up secret keys

Here ya go! (from a friend with android device)
@s0 I love how there’s an Urban Dictionary entry for dQw4w9WgXcQ.
@s0 “can be made read-only: yes” because fixing a rickroll should involve replacing a 20KG chunk of concrete
@s0 what can you 'write' into a NFC chip?
@luka I meant NDEF-formatted NFC. You can write plain text, URLs, contact cards, emails, wifi credentials, etc. Many will automatically open when scanned by a phone.
@s0 i want to play with this. put 'secret' urls to music or maybe club-membership based on the hashed url or something... for (digital online) music and art...

@s0 found a shop and apps to work with chips...

https://nfc.cards/en/

NFC.CARDS - NFC cards, NFC tags, NFC readers, NFC software

NFC.CARDS shop: a wide range of NFC products like cards, tags, tokens, keychains, NFC readers, software...

NFC.CARDS
@s0
@mike
That is crying out for an Easter Egg hunt. Clues written to each NFC hinting where the next NFC can be found and people going around collecting the clues.
@s0 @mike Interesting. Got a pic of these new lids?
@s0 … I wonder how sanitized the NFC data is on the chain from “scan the ID”…
@s0 alternatively, free heavy-duty NFC cards (emphasis on the heavy)
@s0 I shall have to take some time out of my busy car stealing schedule.