You could certainly do something like this with a pi. But it would be bulkier and probably less secure. But my initial prototyping was done with a Teensy3. It all depends on your threat model.

its great that we are getting access to so many tiny sweet tiny boards. just in case - pi zero: https://www.raspberrypi.org/products/pi-zero/

i was thinking more feature set than threat model. Namely Secure at rest storage and password generator for secure comms. i believe the pi has a hwrnd which is probably the most essential thing for such devices.