U2F Zero is a USB token that works with any service that supports U2F, like Google services. It can be registered with any amount of different services at a time. It works for 2 factor authentication or sometimes even password replacement. No drivers needed. Just plug it in and press a button. It's open source and fully documented so you can build your own or learn why it's secure. Check out the source here: https://github.com/conorpp/u2f-zero. Only Google Chrome and latest versions of Firefox support U2F. Firmware 1.1. There's no longer a bug with using multiple U2F tokens on the same account.