Would appreciate thoughts and comments.
Invented and received 182 USPTO approved claims on an Alert system which basicly involves a one button transmitter on the wrist of one diver, and a receiver in, or on the "Mask" of his buddy diver which would light up, beep, or vibrate to let him know he is needed or wanted.
A more complicated design of this system uses dive computers to share data so you can know your buddy divers stats and he can know yours.
Full disclosure can be found at uspto application # 09/862,914
Thanks in advance for your comments....Dan

Unfortunately, electronics and water have a difficult time mixing. The unit would need to be low cost, small size and dependable. Take look at the Aquatec Scub Alert, which is an airhorn that can be used above and below the surface. This is what is currently being used.