Zero-Interaction Authentication

Leave an operating laptop unattended on your desk and your sensitive data is accessible to anyone who gets hold of it. To limit this risk many users configure their systems to fall into a "sleep" mode after a period of inactivity and ask for a password before the system can be awakened. This constant re-authentication proves to be a headache for many users. Now a Professor and his graduate student at at the University of Michigan have come up with a system called Zero-Interaction Authentication (ZIA), described in this article in The Age, to protect data on mobile devices. The system works by starting to encrypt data the moment the owner walks away from the system. The owners wear a token with a encrypted wireless link with the laptop. If the token moves out of range the ZIA re-encrypts all data within 5 seconds. If the cryptographic token moves within range the system decrypts the information for the owner. The token, which could take many forms, is currently a wristwatch with a processor running Linux designed by IBM.
Slashdot

The snoop-proof laptop - The Age

Sounds like a pretty good way to keep the data on your laptop secure. Usually increased usability comes at a cost to security, however this authentication process seems to improve security on top of making it easier for the end-user.