Judging from the NavPlanner2 screen shot above -- which shows off Google Earth synchronization -- it shares a lot of code with the HotMaps lake planner. But NavPlanner2 has many added features. For one thing, the $129 NavPlanner2 comes on a DVD with Navionics Gold charts of the entire U.S. Plus the Northern Bahamas, and a card reader that can access all data on any current Navionics format card.
SonarChart Live is a Navionics feature allowing you to create new 1 ft personal HD bathymetry maps in real time as your boat moves along the water! It appears as an additional layer over your map while it also gets stored on your device for future use. Connect to a sonar/plotter to use SonarChart Live on the app! SonarChart Live is the most efficient way to enhance SonarChart because your sonar logs can also be shared with Navionics from your mobile and you can monitor the improvements while navigating.