SecKey
SecKey has sunset on 1 December 2021 and is no longer available. Because of Apple introducing OTP support in their password manager.
SecKey provides one time passwords to be used with the two factor authentication of Dropbox, Google, Facebook, GitHub, Proton Mail and many more.
It adds a second layer of security for your online accounts. This works by generating one-time passwords on your mobile devices which can be used in conjunction with your normal password to make your login nearly impossible to hack.
Securely stored in the keychain of your device. When iCloud Keychain is on all your One Time Passwords are synced to your other devices.
The app does not collect information about you. You won't be asked to allow access to your contacts or your location.
5 Star Review
You can’t imagine how great you are! I didn’t use Two-factor authentication on some websites, because they support it only for app, but not for the phone number. I am afraid what if I lose an app on my phone. But now I don’t need worry because your app works with iCloud. So, I can use token on all my current and future Apple gadgets with the same Apple ID. Thanks a lot!
~ New Punisher on 2020/07/27
Technology
SecKey was first build in UIKit. When SwiftUI came along I rebuild the app in SwiftUI, this made development much quicker. Frameworks used: SwiftUI, Foundation, and Keychain.
Design
Mac 
iPad 
iPhone 
Mentioned
SecKey is mentioned two times on a German iPhone news website: