something with which to monitor either my sites or the servers they are on, or both. preferably something that can run on a un*x clone server instead of one of my windows machines.

not worried about alarm function, but I'm very interested in plotting downtime in an automated fashion. ping time function that is recorded would be good also.

I can't really complain about the servers I rent now but I see where I'm going to have to upgrade my whole way of doing things in the future so this might help me make the move.

this is done by some with a script. anything like that floating around?