There are concerns human rights will be breached as police forces in Wales become the first to launch a facial recognition app in the UK.
It will allow officers to use their phones to confirm someone's identity.
It could be used on people who have died or are unconscious, as well as people who are unable to or refuse to provide details.
Jake Hurfurt, of civil liberties and privacy group Big Brother Watch, said the app "creates a dangerous imbalance between the public's rights with the police's powers".