Curate, connect, and discover
When tony found out that Peter can hear heartbeats, he immediately made an upgrade to all of the Iron Man suits:
If FRIDAY senses critical vitals or a massive injury, a deep tone will play from within the suit, deep enough it’s not really audible to anyone else.
Peter can hear it though. Peter can hear it loudly enough that he can’t hear the wearers slowing heartbeat.
Peter didn’t have to listen to Tony’s heart stop.