Highprince of Information is an antiquated title for an AlethiHighprince who has authority over criminal investigations, particularly those of interest to the Crown, on the Shattered Plains.
After King Elhokar's saddle tack is compromised, he appoints Highprince Sadeas to this position to investigate the sabotage.
In Urithiru, the responsibilities have changed to that of keeping order within the city by way of law and judgement because, with the death of Sadeas, Dalinar appoints highprince Aladar to this position. He wants Aladar to establish order in Urithiru and make sure that the highprinces have clearly delineated realms of control within it. Dalinar wants Aladar to build a policing force, and patrol the hallways of Urithiru, keeping the peace, preventing clashes between soldiers.