Server monitor

I'm looking for some sort of web-based program which will monitor real-time the different services on my web and mail servers and send me an alert via e-mail if something crashes. All of my servers are running Linux (Ubuntu, CentOS, Fedora) * I should be able to add servers easily to the program. * The program could be run on each individual system and report to a central reporting system or multiple systems in case the central system crashes. * Logs stored in MySQL database * Run reports (both text and graphical) Nothing too fancy required, even a telnet script which connects to the different services on the various ports. ???