Network aplications

There's Apple Remote Desktop and several VNC applications available (some of which are free).

 

Most likely yes, you will need to find a stealth mode application to do monitoring secretly. I would check into the legality of that first though.

Brian

 

If it's only the Internet you're thinking about, block their direct access and make them (and everyone else) go through an authenticated proxy. Then log what each logged on user is looking at on the proxy.

Otherwise, it very much depends on which country you're in. What you are proposing is actually illegal in several countries.