Caving in remote places is simply tops. But, upon the breaking of bones and the trappings of peeps, the surface dwellers are none the wiser. The code of conduct of course is to let people know where your going and what time your coming back. Meh! Who has time for that! Nothing bad can possibly happen. This is an auto dial-er. Cave rescue numbers are set out by the clubs, lists of people to call in an event. The caver's set up the list of numbers, set a return time, set a message and click the go button and boom! Covered. Cavey good times. The system could be a mechanical egg timer that ticks away as your crumpled body lies cold and wet under jimmy the slipped boulder until zero minute and then the magic happens; a pre recorded message informs relevant people of your destination, party size and expected return time. If there is no answer, then we proceed down the list of contacts until an emergency services call. These systems exist. But cost a lot. This will be a cheap and simple unit.