In response to the case of MH370, an idea which has been floated is that of a device to transmit an aircraft's GPS position. Not specified is whether such a device would be operable by the flight crew.
Among the scenarios suggested to account for the aircraft "going dark" and its apparent flight path is intentional action by someone aboard.
To provide aircraft position (or any other parameter) reporting free of any possible interference by anyone aboard the aircraft would require installation of equipment inoperable by and therefore in a location inaccessible to anyone (crew included) during flight. That means such equipment could never be powered down while the aircraft is in flight.
Have there been/are there currently any regulations which would prohibit the installation of such a device for any reason - e.g. fire safety, possible interference with other radio equipment essential to safe flight (navigation, communication)?