I'd also like to mention that I use my fishfinder/sonar/echosounder or whatever you call it to tell me speed, water temp, battery and charging voltage as well. It's also GPS/WAAS capable and gives some NAV data.
I even play a little with the NMEA interface to my laptop. It wasn't expensive either.
I even play a little with the NMEA interface to my laptop. It wasn't expensive either.