I installed the Fire Boy systems in our trawler. This consisted of the flame and smoke detector, the halon system and the engine shut off (required for diesel), and the CO, propane, etc . All indicators are mounted at the steering stations (cabin and fly bridge). The Fire Boy brand is marine tested and approved by the ABYC recommendations. This system cost alot more than those being discussed but they are designed for marine  and are reliable. You also receive an insurance deduction. Well worth the peace and mind when cruising.Looking for less expensive systems as discussed, for me , is not an option when you and your boat is on the water and require reliable marine built systems. It seems that a lower cost is a solution but will let you down a dangerous road when a cheap system not built, designed for marine use, does not function properly..Your life and crew depends on having the approved systems on board. Low priced crap is not worth it.I now exit my take on this discussion. Leonard Stern, INDIFFERENCE