This grid picker clearly choose squares from the 7 x 7 grid when playing The Pirate Game. At any point, a square may be chosen by a player, and then the randomiser continues with the remaining ones.
There is a flash animation showing which square was selected, big enough to be seen across the room. Each square is also numbered to keep track of the order in which they were picked.
Supplied as .txt
just save it as .html and then you can run it in your browser. No software installation required.