If you slide through and ignore the writing, the linked implant teardown is wild - https://www.tibane.net/research/ledger-nano-x-implant

They did, in fact, appear to mass-manufacture a custom-built flat flex implant with cellular (LTE-M!), eSIM, and everything that hid right inside the Ledger, sniffing the SPI reads to the display to read the recovery phrases it pukes out and send 'em over cellular to the ringleader.

It's an EXTREMELY well built implant. I'm impressed. Multiple revisions, even.

The money's too hot to not build shit like this and slip it into the stream. Even a few thousand in R&D netting a six figure ROI is worth it, getting millions is just the icing.

Custom flex PCBs designed to line up precisely on top of an existing PCB seems to be a fairly standard technique for games console mod chips (particularly Nintendo Switch) these days.

But yeah, putting a cellular modem and eSIM on there is certainly taking it to the next level