It would be very valuable to get the option to kill and respawn processes that are using more memory than a configurable amount. This would help a lot in the case of a leaking app. Indeed, consider the following scenario:

• No respawn: The leaking app ends up taking tons of memory, effectively bringing the server down
• Auto respawn: It might indeed require a bit of CPU time, but the service can be kept up and running

I'm not saying that leaking apps are a good thing. But from a "host" point of view, killing and respawning seems like the best thing to do. This is what Heroku does, for example.