Wow, just reading the majority of the responses am now more than ever extremely concerned with the education system of the USA.
-First - "GPS" - anyone like to try?...let's just key in on the "S" Satellite, something not invented or attributed to a Kennedy, Clinton or Obama or the Internet and yes to you millennials the first one was "Russian" and no hacking or conspiracies. But will give you a hint these "Satellites" are Space Based orbiting the Earth
-Second - Apps - Almost any handheld held device such as a smartphone or tablet has some form of "App" for maps which the database is derived from the good ole government of the USA but is dependent on your cell phone terrestrial towers.
Hopefully now with all of your education that has been funded in part by mine and many other taxpayers, thank you, a light has gone off in your head, unless you have a device such as a SAT Phone, which you may have seen in a movie or video game, your regular device dependent on terrestrial tower based technology are not GPS devices.
Stop reading now if you need a hug, cry or a attach a safety pin to your clothing since you just realized you were again wrong about something important in life.
For those of you who has actually been away from the computer/tablet/smartphone(we have to get a better name for that since it could wrongly imply intelligence on the part of the user), when you are in a cell tower dead zone or out of range the "App" does not work unless you are somehow tethered to an actual piece of hardware that will make connection to one of the actual orbiting Satellites up in space with a clear line of sight, two distinct different technologies.
Now with all of that said, can you who did not respond properly please delete your answers and let someone who has experience with this respond, which may not be me because I have only land based navigation experience and the request was for marine, which for the life of me can not understand why anyone would want to risk their or their passenger lives on a thrown together GPS/Tablet configuration when Garmin and other manufacturers make very inexpensive stand alone devices for that specific purpose, but then again when they get lost it will be the EMS funded by our tax dollars to the rescue and we will never see on CNN it was because they were not personally responsible to have the proper equipment.
Good luck with the search.