Booby traps are a war crime, because they do not discriminate between civilians and combatants, even if you place them in a location that is only likely to be accessed by combatants. And public markets and banks and homes aren't that.

https://theconversation.com/pager-attack-on-hezbollah-was-a-sophisticated-booby-trap-operation-it-was-also-illegal-239360

A booby trap is defined by the International Committee of the Red Cross, the body charged with oversight and implementation of the Geneva Conventions and related treaties on the law of armed conflict, as a “harmless portable object” – but redesigned to contain explosive material. They are a prohibited means of warfare and are equally prohibited by law enforcement authorities.

Who held the pagers at the time they blew up? I used to love to play with my dad's pager as a kid.

Targeting using an electronic device is sigint. These people have families, and the Israeli terrorists murdered children with this attack. Did you read the article?