Symbionts for Mac

From Yves Pelletier:

Symbionts is an extension that monitors the startup process. Symbionts displays the name and number of bytes of memory each system extension allocates from the system heap. The name and number appear beneath the extension's icon, and since the name is usually truncated, Symbionts also displays it in the menu bar. Symbionts even shows the icons for those extensions that don't normally reveal themselves.