An alternate root to the usual "Task Killer". I've used a task killer since I got my phone; but this sounds like a better solution.
Watchdog replaces task killers. Task killers blindly kill all apps on the phone, causing increased load times when they're accessed again, or even loss of functionality if it kills something important. Android takes care of starting and stopping apps on demand. Watchdog will find the out of control ones.
What Android doesn't do is alert on processes that aren't behaving well. They will eventually get killed if something needs the memory, but in the meantime, it can consume CPU and thus battery. Task killers address this in a heavy-handed way, and hurt Android's lifecycle management. They won't even work in Froyo due to changes in the API that prevent the kill feature.