Monitoring tools to use on an account

[AG <computing.account@googlemail.com>]

Hi all

I'm facing a bit of a delicate issue: I have created an account on my 
machine for someone staying with us, and I have strong suspicions that 
he is engaging in on-line behaviour that he is not supposed to be doing.

Can anyone recommend a tool thatb I can install, that can monitor his 
on-line activity - specifically sites he visits and how much time he 
spends on them?  A key logger might also be useful to monitor his 
activities.

I'd need something that will mail me reports to my account without these 
being transparent to him.

Any suggestions, please?

Many thanks.

AG