Futurae offers two-factor authentication for online logins using your Android device. The app, along with the typical passcode-based approach, integrates SoundProof.
SoundProof is a two-factor authentication mechanism that does not require interaction between the user and his phone.
In SoundProof the second authentication factor is the proximity of the user’s phone to the device being used to log in. The proximity of the two devices is verified by comparing the ambient noise recorded by their microphones. Audio recording and comparison are transparent to the user. SoundProof can be easily deployed as it works with major browsers without plugins.