What are the names of some of these devices again? I'm struggling to find them:

A year or three ago I came across various devices that had a private key inside them, holding a certain amount of bitcoin.
I think they ran off external electro-magnetically induced power (like a credit card) to power its chip, which could prove ownership of its key to an external device that had a new-enough copy of the blockchain for verification.
Like a hardware wallet it would destroy its key if an attempt was made to get inside it.
I think they held a HTLC balance for proof of it being able to 'hold its value'.
I forget if they had a way to prove that a particular card was the only card that held that key. (I can't think of one; what would stop the manufacturer reusing the same key on more than one card? Possibly some way on the lightning network or similar? I've no idea.)

I searched for half an hour and failed to find them.
Anyone remember some of their names?

Thanks