The things they are doing at Navionics continues to amaze me.
They just announced a new Android and Iphone/Ipad app that will not only give you chart plotter capability but they also added Sonar.
The app is free but the sonar modules/transducers are wifi and range in price from $130 to $200 deping on which transducer you choose.
http://www.navionics.com/en/sonarpho...e_Android_Intl
The other cool thing they are doing with a variety of name brand chart plotter companies is using the logs of your boats coordinates and depth readings to update their charts. It's called community edits
http://www.navionics.com/en/community-edits.
Pretty clever stuff.