Digits uses phone numbers for authenticating instead of passwords. Users simply insert their phone number, and a confirmation sms will send them the secret code which will be used for signing in.
There have been various complaints when Apple or Samsung released their mobile devices with fingerprint scanners. Especially now that many companies have been discovered that have not been trustworthy with their users data and have been releasing said data to third parties without permission. This can make future users hesitant to use this technology.