The Goal of GruePhone 2.0 is to be able to play a number of text adventure games using nothing but an old phone. This will be accomplished using a small, ARM based embeddable computer called a "chip". This will read the descriptions to the user via a text-to-speech engine, and listen for user input via a speech-to-text engine and feed that back to the game.
The goal of GruePhone 1.0 was to port Zork I (via a z-code interpreter) to an embedded platform, and enclose that and an old modem inside a telephone, so that the game can be played from a teletype, TDD, or old computer with an acoustically coupled modem.
File this under "payphone goals".
One of the things I've wanted to do to my payphone for a while now is put some kind of game inside it, but I was thinking more of a choose-your-own-adventure kind of thing, where your choices are entered on the keypad: "press 1 to get lamp", etc. I haven't come across a script for something like that yet.