If any of these cases apply to you...
...then you should try Lock-ix.

Lockix is a hardware and software combination to lock one or more computers.
Locking is done by storing a key in a flash drive. The same flash drive you carry your data in. Or the flash memory present in your cell phone. Or any other flash device you can interface with the computer(s).

To read more click here
Caracolix | Support | Install | v.1.2.0 - 2010