That's so cool that he's looking out for your well being, amazing intuition!
The head nudging is a brilliant cat trait, when Steve was in his prime he'd head nudge so hard that it would physically hurt, caught me painfully on the nose and in the eye loads of times.
Amazing strength indeed, quite often if the bedroom door wasn't wide open enough for him to walk through, he'd slam into it so hard it would hit the side wall with a real thump, easily loud enough to wake me up, having been succesful in waking me he'd then keep me awake by cleaning himself vigorously on the bed with his high decibel licking!
Reminds me of Simon's cat!
http://www.youtube.com/watch?v=w0ffwDYo00Q&feature=relmfu
Our old cat had one of those soundless meows so she'd open her mouth but hardly anything came out, so she could never get attention by making any noise so she used to bounce on the pillow to wake us up..as she was always a bit portly it was likely waking up at sea! When she went to the vets she used to walk by herself behind the vet to the scales to be weighed past all the people in the waiting room. I really miss those open mouthed looks as she sashayed past heh.