Many people use so called gestures on Android to protect their devices. The user interface is designed to be used on touchscreens. It shows 3×3 grid of dots that can be connected by a line drawn by a finger or mouse pointer.

I suggest adding option to protect the session using the gesture, maybe with user-configurable size of the grid.

This could be done completely independently of the OS's authentication model (PAM etc.). On login, normal system password would be used, but then, for unlocking the screen (i.e. not by DM), the gesture could be used instead.

The question is, how to store the gesture data? Plaintext (mode 600 file in home directory) should be safe enough, because whoever has access to the disk can change the even other files and access user data. A file encrypted by user's password would be better.

A notice about that the gestures are not very secure would not be bad.

Also, other “alternative” unlocking methods could be added: e.g. PIN.