Well, I wanted exactly the same for my kayak, and bought a Lowrance Hook2-5 Splitshot HDI with the Navionics+ card included. The Navionics+ doesn't work right on the Hook2, and the SonarChart Live feature does not work at all. So now I am using C-Map Genesis social maps, and I recommend them for Lowrance, since its part of the Navico company now. The Hook2 2D and DI works pretty well, I must say, but the problems I had with the mapping (that CS could not resolve even after I sent the unit in, and then said it might be fixed in a future update) and the poor CS has kinda turned me off the brand.
"Alive without breath, as cold as death; never thirsty, ever drinking, all in mail never clinking."