Floating Action Buttons

Hi Everyone--
I've been asked if there is a way to implement accessible floating action buttons (FAB) as in Google Material Design.  
An example would be a floating map button that provides directions. Another would be a floating link that takes the user to the top of a page (leaving aside the potential confusion if it is styled like a button).  
There are pros and cons to using them, but it would seem to be a problem wrt accessibility.  In particular, how would a keyboard or screen reader user navigate to an object without a fixed location?  I thought of accesskeys, but their use is frowned on because of potential conflicts with shortcut keys.  Having an FAB appear after a number of keystrokes, time, or sentences sounds intrusive and arbitrary.  Putting them in a fixed position on a page seems to defeat their purpose.  I also thought of claiming equivalence if there is an existing keystroke that accomplishes the same thing, but that doesn't feel right.
Am I missing something?
Any help would be greatly appreciated.  Thanks!
Mike Elledge