It’s become quite trendy to have some form of biometric security on your computer now, including fingerprint recognition on your laptop. One solution that sounds like it might work for non-critical security applications is face recognition.
The Snappy Face Recogniser is a webcam which claims to have advanced face recognition technology built-in that will restrict access to your PC unless your mug is present to log you in and access your files. It has a 1024×768 resolution still camera (640×480 at 30fps for video) so can capture a pretty decent image with which to work.
It’s compact and lightweight (80 x 40 x 18mm, 120g) so could be used with your laptop, or as a webcam on your existing computer. It comes with Face Recogniser Software.
It costs £49.98 so it’s not a bad buy. It might be a pain if you already have a better webcam.