[jiveturkey]

I haven't researched their claim, but my guess is that with something like yubikey you wouldn't know an authentication has happened. with Krypton, there would be a notification pending on your phone. Possibly you would only be able to authenticate if your phone is unlocked as well.

[ithkuil]

My phone locks after a while of inactivity. if I have to unlock the phone, then it wouldn't be zero touch, right?

[mplewis]

When Krypton asks you to authorize an access, you can tell it to authorize that single access, authorize the host for three hours, or authorize everything for three hours.

I typically authorize the host for three hours, meaning for the next three hours I don't have to Touch ID in again.