My take: Israel knew or pushed specific pager model to hesbolah. To make it quick and easy for middleman to modify pagers, they made battery with explosives (BBC reports of 10-20g high explosives, so the best place to hide is battery) and tampered with FW and SW, if pager architecture allows they wouldn't even need HW modifications. How it possibly works: pager gets specific message to devices that are suspected to be used by hesbolah (previous monitoring of paging activity), hacked software and firmware through third battery wire (usually for thermistor) sends specific length impulses to MCU in battery enclosure (3x2mm MCUs are off the shelf components), then MCU detonates explosive with few seconds delay. That would explain few details: hiding explosives in battery is hard to detect, since probably no hardware modifications are needed. Most injuries are to bottocks, heads and hands - those who didn't read message had their bottoms exploded, if they there fast enough to pull out pager and read - then hands and heads would take injuries. Israel had to rush this, because smaller battery means it would be suspicious and examined in long term, probably batteries could be started to be replaced due to short battery life. Also we don't know main objectives of this mission, but what it achieved: taken out thousands of combatants, seeded untrust within hesbolah due to laced devices, severed communication channels, reduced recruitment to obvious imminent danger to being in hesbolah, exposed lots of hesbolah agents. Moral things are dubious, but seems like very successful operation in the short time.