Content (or ad) that knows you're looking at it

nostr:nevent1qqs0yn7h4ll5gqas7mx0h0appt6zgyxw9sxucyhkra46qmgyxghsj3cpzamhxue69uhhyetvv9ujumn0wd68ytnzv9hxgtczyzwfsjus4vqray30jst99uvptn68gr8f8sjh6tg4yeh7a5t92t3ksqcyqqqqqqgpv36dj 

 remote exploit that only triggers when you're looking at it 😅  

 or more stealthy... when you're not looking at it... 

 Heisen-ad.  Doesn't exist while you're observing other things. 

 More biological data. 
Zuck was obsessed with eye tracking.