SMS tag was my 4th year final degree project. The project was based around using text messages and projectors as a form of non permenant graffiti that would allow anyone with a mobile phone to participate.
I used a program called processing that took text messages and scanned for key words and then displayed approriate images, projected onto a wall or building. The project was built to be an open source project to allow anyone to build on not only the code but the image library as well.
