Did you have a look at the st60-multi? It has one nmea in and one nmea
out. It will forward almost all seatalk data on the nmea bus.
Maybe this is a alternative for you when you only want to connect your
pc to nmea.

Hmmm, interesting idea. I have no need (or room) for another display at the
helm. I'm not sure whether I'd have room for (or want) another display in
the cabin. That and the price for the ST60 is a LOT more than what a
seatalk/nmea bridge goes for! But it would provide an interesting way to
get the laptop-out signal in a situation where another display would be
handy. Thanks for the pointer!

-Bill Kearney