The app is available for both Android and IOS, and it will run on a tablet if you have GPS on it. You would have to download your maps while connected to WIFI or cell connection.
I used the app for a couple of different runs I did recently in Naples, FL. This is one I routed from our island house down to Marco Island:
It's very easy to set the route even on my iPhone 4. You hit the ROUTE button on the bottom, then press and hold your waypoints until they appear. Once I completed the run down to Marco Island, I simply selected the route, and reversed it for the trip home (displayed above). The blue dot is the starting point, and the checkered flag is at the end of the route.
The arrow button in the bottom left is the button to track your boat on the route, and the zoom control in the upper right allows you to see as much or little of the area as you like. I've got it zoomed WAY out for the screen shot above. The GOVT button allows you to change the map displays. I prefer the Navionics map, but used the GOVT map on this run. There is also an option to connect a sounder to the software as well. I don't have one, so I'm not sure how it works.
If you notice at the top, it will show you distance from your next way point (I took the screen shot after we were off the island), current speed and ETA (which I didn't think worked all that well ... it was constantly changing as we were moving along).
If you note the "pushpin" markers on the screen: the one you see close to where is says "Tarpon Bay" is the fuel dock I found out about when I got to Marco. The marina I originally planned on didn't have dock fuel as I was led to believe it would, so I had to divert over (it wasn't far). I have a similar marker for where the cars were parked and for the pier where our house was.
The photo icon allows you to upload photos into the system - I
THINK they're posted in Navionics maps for all to see, but I'm not certain of that as I haven't used it yet. But you can make notes and images for things you find in your area that you want marked.