I share the same concern.I thought to myself what if a occupied garage floor shelter is under all that rubble ?
I also know you can register your shelter but amid all the confusion directly after a tornado I wonder how long it would actually take before someone started going down the list of registered shelters and be able to actually get to you ?........I think being basically buried alive scares me more than the tornado.
This is my thought:
Have one of these in the shelter:
And have a whistle on hand for a backup.