Great idea!
I'll add a few HB units. Perhaps once we get a fairly authoritative list together, I will make a sticky and put all the units up in table form.
A secondary set of compatible units is basically any sounder that can output depth as NMEA0183. If you are willing to take a laptop onboard, then this data can be coupled with GPS data from any source (I have used an Android smart phone acting as a bluetooth puck, quite successfully).
Humminbird - I *think* just about any combination unit that has a memory card slot:
597, 797, 997, 1197
598, 798, 998, 1198
I am not 100% sure on the 5XX series, so someone please chime in if this is wrong.