Raymarine makes a software/hardware suite that will turn your laptop into the the equivalent of a GPSNav/Radar control station. But the drawback is that the basic hardware/software set is appx $1600 plus the cost of the computer.
Well, not so bad considering John's comments; but cost of the software/interface/GPS/Radar/Depth equipment adds up quick!! Maybe you could get it for less if you can find it online or used. I would not use this system above deck; unless you had a Toughbook and a way of hard mouting the laptop. It might work well if you had a remote display on-deck and the main computer below decks (but you might not have control of the functions unless you could
rig up a wireless
handheld pointing device; or trackball.
I'm trying to decide which way to go also...