If you buy into a poorly managed building though you are screwed. Many buildings don’t keep enough cash on hand for unexpected bills because they want to keep the fees low for residents. Then an elevator breaks, sewage backs up, someone floods their apartment, and all of a sudden there’s a $20,000 bill that everyone has to pony up money for.
You would have to guarantee those phones would eventually end up in the right person’s hands.
Otherwise if you sabotage 100 phones and only 30 go to your targets, even if you only detonate those 30 there are now 70 phones out there randomly floating around with enough explosives to kill some random person.