Wishful thinking. I don't see how a manually activated beacon which is not the type which works underwater (even if it did survive the impact with the ocean) could possibly help.
Well, maybe... if the passenger carrying it knew precisely what was happening to the aircraft and remained conscious long enough to operate it and the aircraft presented no shielding to radio waves and the batteries lasted the duration of the remainder of the flight...
You missed the mark completely about the Spot Tracker - They leave a breadcrumb uploaded by satellite to a web page or similar with 99.99% accuracy.