System load notification

Hi, Let's say I have a resource intensive process that I would like to be ran only when the system is doing nothing and since another process is starting to drain resources from the system, stop the first one. So I wonder if we can ask the kernel to send a signal to reproduce this behavior? The way I see it is to write a daemon subscribing to receive a signal when the system is idle (or low on load) for a certain amount of time, and to receive another signal when the system starts to be high loaded. Of course the load produced by the process itself should be excluded. Any idea? -- Jimmy