how to access the guid of a currently viewed item from within a view?

i have most likely asked this before. i still don't have a way to do this.

e.g. if i create a view that can be used on multiple pages and is called from it's own start.php file (such as one that adds a module the sidebar on any available page) - i do not immediately have a way of accessing the guid of any entity that may be being displayed on that page. this is limiting the posibilities of what i can code.

my current options are to add the module from within every plugin (blog/bookmarks) etc. to ensire the entity is passed through to the view (which would massively increase the amount of code i write) or i could scan the browser url for the guid (which would work but is not ideal since i prefer to keep these processes internal to the server).

or is there a way of accessing the current item's guid from an internal variable or function that i am not aware of?