A free program for Android, by Bamboo Games.

The Spy app brings another classic party game to your mobile device. Its rules are simple and easy to understand: out of a group of players, someone will be assigned the role of the spy. A single word would be shown to non-spies, then everyone would have to work altogether in determining who the spy is (who does not know what the word is!) by asking word-related questions to each other. The spy will win if they manage to guess the secret word, but they will lose if anyone busts them.

Furthermore, setting the game up in the menu is effortless, allowing you to get to the fun part right away.