I have an X right here, and it usually rests on my desk. It will unlock from a VERY oblique angle, way beyond what i expected it to be able to handle. The only failures i've gotten with the scanner were when a pillow was covering part of my face and i was in bed. Basically any position that i can reasonably read the display from that isn't a joke or a test will unlock the device if i'm glancing at it.

I have some complaints about the device, but this feature rocks as far as i'm concerned