Looks like they are using a proprietary secure element and a closed source required app. Pretty cool though. Lots of reasons and uses for physical Bitcoin. Really interested in your project!

DarrelXero

The offline cash stuff looks pretty cool, I wonder if they're using the same NFC tags or something different. It does seem pretty complicated though with the multisig stuff

 and is probably the most reliable way for a quick chat.

I do have nostr but I barely check it. If you'd like email works as well: 

bitcoin

Mint your own Casascius style bitcoin with $1 NFC tags, new FOSS bitcoin project

justh0dl

The offline cash stuff looks pretty cool, I wonder if they're using the same NFC tags or something different. It does seem pretty complicated though with the multisig stuff

My x handle is @justh0dl and is probably the most reliable way for a quick chat. 

I do have nostr but I barely check it. If you'd like email works as well: j@10msats.net