You Devmon ideas are pretty good. I don't think there is any development going on on it however. It has been stuck at 0.3 whatever for a very long time, on SourceForge. I would change to something else, but haven't found anything.
As to your second question on Xymon.
Also, I've noticed a bug with xymon dates, currently if I disable an alert and I select say 6 months out, it marks the times as something nonsensical. For instance, I currently disabled a few hosts and chose disable until November 1, 2013, and they are saying disabled until Sat Jun 14, 14:13:44 1902. At some random time, usually a few days to a few weeks later, they re-enable themselves, which is annoying. I just read the 4.3.9 through 4.3.11 release notes, and the 4.3.9 release notes state "Fix error in disable-until-TIME or disable-until-OK code" Does this fix address the same bug I just described?
We ran into this, but our setup was a bit unique. We have two proxy servers that also operate as backup servers. So they have the proxy function that sends to the primary server, but they also have a server function on port 1985 that the proxy also forwards too. That way if the primary goes down , they can take over.
So there is a mismatch on how dates are handled in there somewhere. And we added to our disabling on the primary to inform the secondary's, i.e. sending the message on. Well, with the difference in handling the raw date data, we got into a cyclical issue of the primary telling the proxy, and the proxy sending it back. If you watched it, the disable time changed multiple times until it cleared itself.
We upgraded to 4.3.10, but it still happened. Then I figured out, we don't want to tell the proxy, we want to tell the server. So we adjusted the primary to send the disable message to 1985 instead of 1984 and all was well.
So, in short, 4.3.10 does help in this issue, and may fix what issues you have, but you may need some other work.