The NTAG I2C chip used in the SiiD module we used to construct the xSIID implant has 2kB of memory, split into two large memory sectors. The problem is that the NTAG I2C chip is not commonly used by consumers, and at the moment there are no apps available that properly identify and read the entire user memory beyond 1kB. Please read this forum post carefully as it explains the issue and possible remedies; https://forum.dangerousthings.com/t/so-what-happened-with-the-2k-memory-on-the-xsiid
It’s not like the Apex which can be updated so the flexUG4’s functionality will not be expanded beyond the capability of the chip. The lua script that configures it supports most of the chip’s functionality but not some of the ultralight options–so there will be more easily accessible functionality at some point in the future beyond our control. Regarding DESFire, no. I wouldn’t expect that to be a thing, unfortunately.