Joshua Aaron has worked in and around the tech industry for around two decades. He built his first app — a blackjack game — at computer camp when he was 13. His newest app is designed for a very different purpose: to let users alert people nearby to sightings of Immigration and Customs Enforcement agents in their area. Aaron launched the platform, called ICEBlock, in early April after watching President Donald Trump’s administration begin its immigration crackdown. The White House’s immigration policies have sparked mass protests across the United States; a CNN poll in April showed 52% of Americans polled...