You can buy the xNT NFC chips from here: https://dangerousthings.com/ https://dangerousthings.com/ There is no secure element in the chip, so it can not direct

You can buy the xNT NFC chips from here: https://dangerousthings.com/ https://dangerousthings.com/ There is no secure element in the chip, so it can not directly replace a yubikey. It could however hold encrypted data or be used to replace car keys etc. When it comes to physical access I normally just authenticate using the devices hard coded UUID. This is at least significantly better security than a traditional metal key which can be trivially picked. I modify things with NFC Reader/arduino/relay setups to read my UUID and start/stop lock/unlock things such as my motorcycle. You also have 1k of read/write storage so there are a number of interesting possibilities there. Mine often contain my info as a vcard so anyone can tap my hand to import my contact info. Or sometimes it might launch a rickroll. The magnet has been really interesting. I am constantly finding EMF around me. Knowing if a power strip is on without fiddling with it, knowing if wires are hot without touching them, knowing when I fill up a soda cup exactly where under the counter the motor is, knowing where transformers are in walls. It is I admit mostly a curiosity, but I have learned to use it as a tool instinctively. When I am trying to hold screws up in hard to reach places, when I have lots of tiny screws I need a secure place to hold, or when I drop a screw in a spot just big enough for a single finger to reach. I don't even think about it anymore. It is just like "oh I have this tool" or "oh there is EMF over there". It is interesting how the brain just starts to accept new abilities to the point they can be used passively. It also has some fun side effects. For a while I thought the compass in my smartphone was broken. Had to learn to stop holding it in my right hand. I can "feel" music if i put my finger near a speaker. Hard to describe. Equally hard to describe is when I encounter a string magnet and the magnet under my skin flips. It is... not painful, but certainly not enjoyable. Would do it all over again though.