The item in question is a Humminbird SmartCast.
I have one and it works, sort of. It will give an image of the water column. The problem is that the width of the cone of area being examined is very small. It may take MANY casts to get a feel for a particular area and even then you have to remember what the previous casts looked like.
My feeling is that it's better than nothing. I found one piece of underwater structure with it that has produced fish. Wouldn't have found it otherwise.
Note: reel it in VERY slowly.