Security products to lock a user out of their computer

[JGrimshaw () ASAP com]

I am looking for information on any security product that could lock a 
user out of their computer--such as a remote user with a laptop, that has 
been terminated. 

Does anyone know of such a product?

Thanks for the help.   I have searched with limited success, and am 
waiting back for replies from various salesmen--but I figure the list may 
have some unbiased experiences to share.