More and more, I'm recommending that friends and family get a Mooltipass[1]. It's open source, it works on any platform that supports USB HID (including mobile devices using an OTG cable), it's got multiple browser plugins, and it allows you to have "two factor" auth by seperating the pin-protected crypto key from the device itself using smart cards.
The device can be backed up, and the cards can be backed up too (since unfortunately it's not doing the crypto on the card, the card is just a verifiable pin-protected way to store the AES key) and it's an obscure enough looking device that it's not yet an easy theft target.
If this thing fit on my keychain, I'd strongly consider it. I can't see carrying a card, a device and two usb cables around, which is what the current form factor seems to require for use with my phone and computer. Maybe a usb key with a screen, bluetooth radio and battery would work.
The device can be backed up, and the cards can be backed up too (since unfortunately it's not doing the crypto on the card, the card is just a verifiable pin-protected way to store the AES key) and it's an obscure enough looking device that it's not yet an easy theft target.
[1]: https://www.themooltipass.com/