As Time's sources inside Amazon explained, the feature would use a "voice print" to verify each speaker's identity and primary account holders could set Alexa to require their voice print for specific commands. That means that the person with the credit card tied to the account could set their Echo to require their voice for purchases and restocking the fridge.
The Voice ID feature, which has reportedly been in development since 2015, could also help ease some of those Alexa headaches and accidental shopping sprees. While Echo speakers currently allow for multiple profiles, the Voice ID feature would allow different users to access their accounts without having to switch between them. Time's sources say the feature is currently completed, but it's unclear when it will actually get integrated into Echo devices or if it will require new hardware to work.