I have an electronic one fitted to Bayshots. Not beause I really needed one, but they were giving them away as a promotion;so I thought why not
It plugs into my Matrix 87C and I mounted the sensor just below the wheel for protection.
You can display a total page showing history or as an icon on the bottom of depth or navigation displays.
I find it useful if you are planning on sitting on the water all day fishing or the like.
There was a funny story just after I had it, and went to the montains lake fishing. It displayed black clouds and dropped dramaticaly and yet it was a clear sunny day.I waved it off as a cheap gimmick and ignored it . 3 hrs later the biggest thunderstorm in 10 years hit us
My boys never let me live it down