Make your own smallest device with full android. I use this for Google Authenticator application. Just be careful when removing the wrist strap. There are antenas. You can cut it or disassamble it a bit and remove it properely - just to be able to make a smartwatch again if needed :)

EDIT:
I edited the knob because it was too high. You can use it if you like to feel big knob. My goal is to have it as minimal as possible. So you can use the v7 version.