I do this process by downloading subtitles automatically with http://subdownloader.net/ or manually from http://www.opensubtitles.org/en and then play the tv series directly on the tv.
It's of course less advanced than this (but more easy/enjoyable). I think this approach could be good at the beginning of the learning process (i.e. I've just begun studyin' French and it's too difficult for me to watch a movie with french subtitles only)
EDIT: it's a pity it's Windows-only (Mac in the future) I'd like a Linux version or better a XBMC plugin :)
Now there is! Seriously, although there are alternatives that do part of what your player does on Windows/Mac, there is nothing of the sort on Linux. Definitely make it cross-platform.
Yeah, I'd pay for something like this (for Linux) for learning Spanish. I learnt English by watching TV, and it's pretty much one of the best ways to learn a language.
A small problem is that you'd have to find enough good Spanish (as in Spain) shows/movies, but I guess there's no dearth of those.
EDIT: it's a pity it's Windows-only (Mac in the future) I'd like a Linux version or better a XBMC plugin :)