Killing Notebooks

These days the problem of losing notebooks is common. The size and mobility of the gadget makes it easy for someone to just carry it away from the owner unsuspectingly and easily hidden. With detecting gadgets, the presence of notebooks is easily located even if it is hidden especially in cars or offices. I am not very educated about electronics and when a friend asked how can it being detected when the notebook is switched off. I gave the answer that the notebook has a battery for its system clock. So, the presence of electronic waves in the notebook makes it detectable. Er...am I right? 

Since notebook theft is unavoidable and losing it includes losing all the content which might contain private and secret informations, makes it more important to increase its security. 

Tonight I found an article in Digg "Lenovo Kills notebook with a text message". 

Thinkpad laptops will allow notebook owners to disable a notebook with a text message that is sent to a 3G-enabled system via a cellular network. The lockdown will happen immediately if a notebook is turned on or, when it is turned off, the next time the system signs on to a cellular network. To reactivate the disabled PC, a user needs to enter a pre-set passcode created during notebook startup.