You know Android uses a limited set of fonts and you know how those fonts are rendered (by freetype - <[url removed, login to view]>)
You also know that you can easily capture screen shot in Android (by following this <[url removed, login to view]>).
Now we ask you to identify all characters on screen (say, by comparing fonts to fonts).
You could say this is a special type of 'character recognition' (OCR).
Let us know if your approach is language specific.