You should check out FoCal Pro from http://www.reikan.co.uk/focal/ It is cheap for the results that you can get. What is the point to have a $3.5k body + a $2k if your set is not calibrated? Also, AF Info tab on the site provides a good explanation how MA works.
I use LensAlign & MA all my primes. FoCal is an automated way to do what I do manually... which is cool; I'm glad someone developed an automated system. The 'AF Info' tab doesn't provide anything we don't already know... in fact, he emphasizes calibration btwn AF plane & sensor plane -- but that's corrected for by the 'All by same amount' option under MA, not lens-specific MA.
He himself mentions that the -20...+20 numbers don't have much inherent meaning. That's b/c right now, to most of us, MA is just a black box. And as many of us have found, one MA setting is not accurate for all subject distances.
Way off topic here.
Ok, sorry... I just ran with the example you'd provided in your post.
More relevant to the actual topic: As much as I'd like to see this sorta thing happen, I doubt Canon will want to be liable for all the potential problems. Apple has a review team that reviews each app; Canon would have to have something similar if they didn't want apps to mess with their cameras (calling for more repairs).
Also, imagine some added functionality that uses a poor resource-intensive algorithm that slows down the camera's performance. That could generate bad rep & more headaches... after all, right now high-end Canon bodies are known for their speed, right?
So as much as I'd like to see some sort of an 'app store' or firmware access, there'll have to be some new & interesting model that allows freedom of development yet is restrictive in terms of how much it can mess up camera performance/reliability.