Monitoring a specific virtualhost apache
Monitoring apache quite easy. There are plenty of solutions to do that. When it comes to monitore virtualhost one by one, it starts to be difficult. Of course, there is always the solution of using stats softwares but usually, it is not really time and doesn't give a quick and efficient overview.
Here comes mod_watch. A quite old module for Apache (1.3 & 2.0). Basically it monitores the incoming/outcoming traffic and the requests.
There is no debian package for this module. However, it is very easy to install.