The company I work for sells Spector Soft's "E-Blaster" software. I've heard lots of good feedback regarding it. It will monitor pretty much all activity on a pc, and send it to a specified e-mail address on a user specified time basis.
However, I have not been afforded the chance by the company to personally install it and test how well it hides itself, or personally seen how well it performs the functions it claims to perform.
But I've never heard any negative feedback from any of the customers we've sold it to.