Apps save text from outside my app

[yotam2010]

I want to save each word the user write either inside my app or outside (when my app is either in background / not open) in local database (sqlite). I assume I am using service that recgonize spaces / dots / enters and then capture the word before this char but how do I actually capture the word?

BTW
It might sound like some kind of malicious app, it isnt. I want to make some kind of dictionary.
Thanks in advance.