A bit before your time perhaps, but our best mod was a Decca repeater in the cockpit (circa 1990). No more going below every few minutes to check where I was.
Thing I most appreciated was when we used a lappie for nav, and we connected a cheap TV (12v) to it with a long lead and positioned the tv on deck inside the windscreen so we had the chart on deck so we could watch it while pressing the autohelm buttons. (Often wondered what that wheel thing was for).
Fab for harbour approaches in poor vis or at night. So simple too. /forums/images/graemlins/grin.gif