Not what you'd think – Marco Polo: Find Your Phone by Shouting MARCO! Review

Sadly, this app does not live up to the hype. It is continually polling your mic, and so there is constantly a bright red bar at the top of your screen reminding you that it's eating up your battery life. If you don't like that, you must disable the app, which makes it useless for its advertised purpose. The voice recognition is incorrectly trained so that it will fire off of any word beginning in "mar", and the sensitivity drops off markedly with distance, once again crippling its primary usage scenario. Neat idea, but I do not believe the current OS and APIs make it possible to use this app as advertised, and it is only notable as a novelty.
Review by CurmudgeonlyReviewer on Marco Polo: Find Your Phone by Shouting MARCO!.