I also had to buy the ~$60 Lowrance "NMEA starter kit" which is how everything connects together. My total purchase consisted of the HDS-7 Gen 2 radar package, Point-1 sensor, and the starter kit. Just over 2 boat units.

It still seems a bit amazing to me that, even with the boat sitting on her mooring and not moving, the unit displays our heading to the exact degree. One of the Lowrance salesmen told me the Point 1 contains the same technology as something they sell that is quite a bit more expensive, but I don't recall exactly what that was.