Since GS 3.1 you can do that without a plugin. Instead of get_page_by_id you could use the built-in function getPageContent (more info here: http://get-simple.info/wiki/config:caching-function )
(AFAIK the only difference is that SimplePageContent's function doesn't run the content filter)
(AFAIK the only difference is that SimplePageContent's function doesn't run the content filter)