How is it any different from Google Maps' "Police Reported Here" feature?

In the U.S., sharing the location of police officers is generally protected by the First Amendment, as long as the information is obtained legally and is publicly available. This is why apps like Waze and police scanners are lawful and widely used.

For an act to qualify as obstruction of justice, there must be a clear and intentional effort to hinder or delay law enforcement in the investigation, arrest, or prosecution of a crime.

Since that's obviously the intent with this app, it's relying on a thin veneer of plausible deniability.

So would using public street cameras to track known ICE license plates be legal?

apparently the developer has consulted attorneys on the matter. in any case, i would have thought that simply reporting an officer's presence is completely legal as you aren't really obstructing them