I was thinking about creating an anchor alarm app. Basically when you start the app it will get the position and let you press a button to fix the anchor position. As I think of it, you arrive to an anchorage, you drop the anchor and press the button in this app (that you have opened before, so it gets a fix). Then you can configure a radious and it watch will beep if you go out of it. Also it will have an option to plot the positions since the alarm was set in order to see how the boat has moved.
I will have to work with the PSMOO gps power mode so the battery lasts at least one night.
Anyone is developing something like this? Do not want to make twice the same thing :)