http://www.discountdivers.com/…isea.horse.collar.bcd.jpg
this is what my dad used in the 80s . it is horse collar bcd with co2 rapid inflation , manual inflation and quick purge valve . he use to put 2 breaths into it to allow him to stay still and rest [ like a pillow ] then when he wanted to dive he will press the purge valve which purges air from the top of the bcd making it deflate quickly and if at depth and about to black out you can pull the co2 tab to rapid inflate and it does keep you on your back . once he was pushing himself too far and blacked out right below the surface but because he always kept a little air in it he floated to the surface and woke up . it is not as good as a FRV with the dive computer because it is manual but it does provide a B plan for a good price [ around $200 usd ] but it is a little hard to find these days . if for nothing else it can help in the situation of a cramp , loss of fin or just to rest .[ by the way how do you post an image from the internet .]