Are you looking for keyword-spotting software? sensoryinc.com has been doing this for years, and only recently made some Android apps. Here is an example in which I'm driving and want to use a voice trigger to record an audio note. Only after I say "hello blue genie" does it start recording my audio note.
http://vimeo.com/64658273
(no I don't work for Sensory but I think their tech is greatly underappreciated)
