my mom attempted to use a program called "PC Tattle Tale" on me. It was 50$ and keylogged the computer so she could get on my myspace, IRC, ect ect. Needles to say, I was PISSED when I found out. Unless you want your kid to take your video card out of your computer till you agree to remove the software, I wouldn't suggest doing it.
Or are you concerned with the content he may be viewing?
If you're concerned with him viewing things that are NSFW (porn, 4chan, ect) sit down with him and have a nice, long, awkward talk and he'll be scarred for life, that should work!
If you're just curious, kick him off one day while hes on it and look at it then