The existence of this technology means that ICE can grab anyone they want, scan their face, and instantly have (or not have) probable cause to arrest them. Without the app, there would be hours before probably cause could be established which makes justifying the detainment legally much harder. I.e without the app, ICE has to actually build a case or see something suspicious for each target. With the app, ICE can just mass sweep people.
Which should be illegal, but thanks to the shadow docket order on Noem v. Vasquez Perdomo, is happening anyway.