Earlier this month I mentioned I had an Android phone.
The first app I purchased was Navionics Mobile which give me a chart plotter on my phone. The cost was just over $29.99 which included the charts for BC.& USA, Marine & Lakes This app also gives you the tide and currents. This is an amazing bargain considering the charts for BC and Alaska are $249 for a full sized plotter! This may be purchased through the Android market.
Navionics also has apps for the iPhone and iPad. I was instructing a couple last weekend on their 28′ Bayliner and they were planning on purchasing this software for their iPad. At this point, they do not have a dedicated GPS chart plotter aboard.
However, remember you are legally required to carry paper charts aboard your vessel.
More information on the Home Study Coastal Navigation course.