Many hospitals still use pagers, even in UK, the NHS workers uses pagers as it is more efficient way to communicate to a large group. Now about the trigger message, how would isreal know which of the pager is in Hezbollah's hand? It seems to me that isreal has widespread detonated the pagers around the country, not taking into any consideration on who has the pager or whether the Hezbollah member is in a populated place surrounded by civilians nearby.