This is the program I use to monitor for run away programs:
Watchdog Task Manager - Android app on AppBrain
Essentially, the program takes a "snapshot" of CPU and memory usage at intervals you decide. If a program is detected as using too much CPU or RAM, you are given a notification and asked, "What do you want to do with this program?" Ignore or KILL. This is all I've ever used and as long as I'm in a place where I get a good signal and don't play too much Angry Birds. My battery will last all day.
It's just a couple bucks and there's a lite version too.
When I was reading up on Android memory management, I came across a great saying to describe it. "Free memory is wasted memory." Get out of the Windows XP mentality of memory management and welcome yourself to 2010 Android!