Blender has the ability to draw text in the game engine using special bitmap fonts textures. These bitmap fonts can be created from a TrueType or a Postscript outline font. For an explanation of how to create a bitmap font look for the Tutorial How to create your own bitmap fonts on the Blender site.
To get bitmap text or numbers displayed on a single face you need a special bitmap with the font rendered onto it. Then create a property named "Text" for your object and map the first character ("@") of the text-bitmap on it. Check the "Text" face attribute for the face Paint/FaceButtons. The property can be any type, so a Boolean Property will also be rendered as "True" or "False".