Well, the smallest I can think of short of a device designed specifically for cellphones would be a USB fob and an OTG adapter.
I’m not sure you could go much smaller anyway actually, as the device needs to be large enough for the antenna to have any kind of efficiency for implants - especially HF readers. And you want a cable, as something with a fixed MicroUSB plug that isn’t really, really small would easily bust the socket if you’re not super careful all the time.
That’s what I do when I want to check LF chips before and after implanting them at my piercer’s: I bring my cellphone, this teeny tiny wedge and a short OTG cable. Both the fob and the cable fit in a matchbox.
I found this.
It can scan a tag from the keyboard and confirm the entry. It does add spaces instead of a colon. Not able to tinker with it much at the moment since I’m at work, not a good look to have a confused expression while staring at my phone for too long.
I’d probably just make a custom app that lets you copy the id in your wished format.
Then when logging in to a website, scan, it asks if you want use the “new tag” ndef thing or copy the id to clipboard.
Doesn’t sound 2 hard… theoretically.
someone could probably update to work with android phones over a network or bluetooth connection… oh but it uses sendmessage windows API to “type” stuff… so probably can’t use for login to windows since that’s a protected dialog box.