I couldn't tell by your code whether it updates constantly, but you may be interested in linux memory leak monitor. If you have an xserver running on the apache machine, it will open a little Tk window in the bottom right corner, and update it every second. That way you can watch it over the day, just with a glance.

If you need to run commandline, you could run your script under POE or even Roll your own Event-loop where you can setup a Glib timer. (Of course, you can also put it in a simple loop where you run it, then sleep 5) ;-)

But feel free to modify my MeM script, and add all your info into the Tk Label.