Check Login from page outside of Contao

I am looking at setting up a php page that can check if a user is logged in to contao, yet isn't embedded through Contao's file system. Is this possible? If so, is there some special php code that I would need to use to check if the user is logged in and then get the user's credentials? Reason being I would like to create the page at a different subdomain than the main site is at, in order to make users able to access the page easier. Instead of trying to remember the domain/pagetitle.html just remember title.domain.ca
Hope this makes sense.