Each Z-Wave Device and Plugin Instance (not counting child devices …) uses about 4MB of memory. If you do not have a USB disk for the logs … then the logs are stored in memory as well.
Might be time to put your Vera on a diet!
Remember the Heisemburg Uncertainty Principle … if you try to add a plugin to monitor the state of Vera, you will be consuming the precious memory your are trying to monitor.
I suggest you login to the machine via SSH and
check the results from the unix command free and df