We all know very well that username+password is a very weak form of authentication. Unfortunately alternative universal and more secure methods are not available.
Some researcher (see here for example) are proposing to use our mobile phones as pencils to draw our signature in the air and to use this movement as our password. This approach has many interesting characteristics, from the hardware-set used, to the movement itself which can be extremely difficult to replicate, much more difficult than a fingerprint, and a few drawbacks like the obvious need of space to do it.
There is already an App for Android that you can download here. In any case, more research is needed in particular in the full evaluation of the security features of this almost biometric authentication method.