I am with with you, thinking that a watch that does the barometer, compass thing would be helpful. To those who might say it would not be accurate enough to be useful I say "pish posh". Let's assume that the watch has a LARGE/HUGE (+ or - , 7%) error in both pressure and magnetic compass.
You are in your dingy poking around some little islands near your anchorage in coastal maine when a fog bank rolls in and your ALL TURNED AROUND and the current is carrying you in who knows what direction? Which way do you row ?
You are sailing coastal and are passing the last good inlet/harbor for ..."a while/ a good ways" when you glance at the barometric pressure and see that it has been dropping steadily and fast for several hours. ?? What to do ??
Even if it were true that the actual reading of the pressure and direction was off a bit, it would not make it less useful in these two cases. I believe that most wrist units today are more likley in the WILD GUESS=> (+ or - , 1 or 2%) range.
Now I am being sarcastic when I say that (a) most folks probably keep a survival kit including compass in thier dingy when cruising and always review a chart and tide/current tables before poking around in the dink, and (b) those same folks religiously note barometric pressure and trend in the logbook every hour. Ha! Having said all that I don't have such a gizmo.
However, every time I go to Walmart I make it a point to pass by the watch display in the jewelry case to see if the compass watches have gotten any smaller and if they have barometer/tide. Casio and Sunnto are the main players doing wrist watch fancy computer gizmos but their are a few others. It is the fact that they have been SO DARN BIG, almost like wearing an alarm clock on your wrist that has kept me from joining the club, but I keep looking and I know that in the next 12-36 months the market place will provide what you asked for and more in a both a small form factor and at a price point that will bring them into Walmart.
As for computer interfacing the ones available ??tomorrow?? will be wireless capable and will likely serve as interface/display into your boats data system (e.g. TackTick) and will talk to OsX, Linux, Windows Vista and your kids $100 laptop.