I don't know, but I do know that back in 2013 you could get an ARM computer running linux and a webserver with wifi and 16Gb storage in a space the size of an SD card. That is still a bit too big to fit inside a USB plug without being obvious, but not by much. https://hackaday.com/2013/08/12/hacking-transcend-wifi-sd-ca...
Fitting the electronics inside the usb plug itself has been used for years in slimline usb memory sticks and in tiny readers for micro-sd too.
I expect that this has been possible for nearly 10 years, but maybe just not commercially viable for consumers for most of that.
I'd say the total size of silicon has been small enough for this for at least 20 years. The level of integration between these components, skipping the need for packaging and interconnect is what's allowed these covert devices, probably driven by manufacturing optimization that makes is financially tractable to only make 100 units, so that bit is much cheaper yeah. Things like antennas and other bulky non-silicon passive components are probably the limiting factor now.
I don't know, but I do know that back in 2013 you could get an ARM computer running linux and a webserver with wifi and 16Gb storage in a space the size of an SD card. That is still a bit too big to fit inside a USB plug without being obvious, but not by much. https://hackaday.com/2013/08/12/hacking-transcend-wifi-sd-ca...
Fitting the electronics inside the usb plug itself has been used for years in slimline usb memory sticks and in tiny readers for micro-sd too.
I expect that this has been possible for nearly 10 years, but maybe just not commercially viable for consumers for most of that.