LinuxQuestions.org - Remote Server Monitoring

I've been looking around for a better way to monitor my Linux servers across town and i haven't come up with anything that really does the work i need so i was wondering if anyone could throw in an advice. What i need is a software either Win32/Linux(preference is Linux based) that can monitor remotely any count of servers. Something like GFI Server Monitor looks like what i'm looking for but hey 10server = $499 -=> mmmmk no thank you :D. What i wanna be able to monitor is:

1. Apache up/down
2. FTP up/down
3. Host up/down (ping based i suppose)
4. Sendmail up/down
5. Quota warning

and so on and so forth. Of course if any of the services i'm running on a given server stops i wanna be notified by SMS, pager, email. For a stand alone system i'm using this really simple but useful script from:

phpSysInfo
http://phpsysinfo.sourceforge.net

For GUI other than SSH control:
Webmin - Web based Control Panel
http://www.webmin.com

any ideas would be greatly appreciated, tnx.