Wrist watches have the advantage of having the information in an easy to access spot and eliminating extra hoses. If you have a computer that will allow a transmitter, the watch will even display your tank pressure and dive time remaining based off of air consumption. The compass would then be worn as a watch on the wrist next to it or what I prefer is to have the compass on a retractable lanyard connected to the BCD. Suunto does have a watch that also has the compass built into it, but the number one complaint I hear about it is that the compass is more difficult to use then a standard compass and not worth the extra money.