Regardless whether this is the function or not, you've hit in a great idea. "Tap for bookmark".
Thanks!
Apparently posting in this thread has also raised my number of likes received. It's THROUGH THE ROOF. Thanks, DiveNav.
To continue:
5) Your bluebuddy vibrates when your buddy presses a button on his/her bluebuddy. Gets your attention without making a racket.
6) Your bluebuddy lights up when your buddy presses a button on his/her bluebuddy.
7) The bluebuddy is now some sort of emergency missing-diver-location device as well.
8) The bluebuddy is now random-colour-of-your-choice-buddy. It changes colours faster than a cuttlefish when shaken or tapped hard. It can also squirt ink to confuse a potential predator.
9) It is now a disguised underwater handheld weapon to prevent illegal reef fish collectors from snatching the regulator out of your mouth while you were policing the waters (or after the fact). http://2sb.us/482868
10) It protects the bluebuddy from knocks and shocks when diving, giving divers the alternative option to hold it. Nothing more or less.