If you've got net access (or even if you don't), it seems almost plausible that you could just identify the book/page in question and use a lookup table of coordinates.

I don't know how many variations on the /Where's Wa[a-z]+\?/ theme have actually been produced, though, so maybe it wouldn't be easier.

Then again, if you can upload unknowns, wait until you've got enough samples to generate confidence, and then store the result, it'd scale/perform much better :)