After seeing the video clip posted by Brown mullet. (Samba and Blackout)
i was thinking of a life-vest powered by a co2 cannister, like the one on airplanes, whit a tricker set to your max the maximumdepth and maximumduration for your dive. Good idea´r ? i thought i was. but some one beat me to it.

look at this link.
http://www.oceanicss.com/index.htm


http://www.youtube.com/watch?v=vNMlQI_0BJU&feature=player_embedded


but at the price 2.800,00 usd, a bit expensive if you ask me.