There is already an API available to do this today. The Microsoft Cognitive Services computer vision API detects words, phrases, and lines and included bounding box information indicating where the text was found. See https://azure.microsoft.com/en-us/services/cognitive-service....

OCR excels at picking out digitally generated text, but it's not so great at "real world" text unless you help it by zooming in.

For example, it can't tell there's text in this clear image of a VIN:

http://1eask1khnn22hm3njx2dmz1a.wpengine.netdna-cdn.com/wp-c...

But I bet if you took a closer picture (like you would if you were using an AR app) it'd work