A group in San Diego is patrolling neighborhoods to identify potential ICE presence. They keep watch for vehicles that may belong to federal agencies, and use livestreams, radios, and social media to keep communities informed. 

Bolts
How Volunteer Patrols Are Working to Protect San Diego Immigrant Communities From ICE - Bolts
In the early-morning twilight on a cool Friday in April, a half dozen people gathered in a small parking lot in the San Diego neighborhood of City ...