The Lockheed P-3C Orions have had the airplane locator beacon system for years, I first saw them in 1986. Admittedly, it's only the 243.0 and 121.5 homing signals that are transmitted, but it sure beats the current locating system, as in MH370!
There are 6 sensors located in strategic parts of the airframe, like wingtips, nose, tail and wing centre section, any one of which will trigger the release of the device if 'smashed', or simply released by a switch in the flight deck.
The device is aerodynamically shaped, and will 'drift' down to the surface when released, and of course, it will float (low in the water, so as not to drift too fast)
The device is spring-loaded in place in the vertical stab (RHS), and released by a mechanical latch which is battery powered.
All this is designed to find the airplane, nothing more!
It's designed to be located immediately via satelite, before it drifts to far!
And, I've never heard of one accidently being released.