need good monitoring software
hello,I need a good monitoring software, it must monitoing services and send me a mail it one or more fails.
My current sw send my to much wrong alerts (it say apache failed but apache still runs and was never down etc etc) so I have disabled it and now, one day later, my main host crashed and I noticed it 4 hours later...murphys law

I lost some clients and now I realy need a better monitoring sw, I wrote a little shell script which make a dubble-check (if one service fails, it check it again and if it fails again it send me a mail) before it send me an mail but my script is to basic.
Do you have any recommendations?
Thanks