The traditional interpretation of the both Eastern and Western Church has been for the first fifteen hundred years (before Protestants started to deny the belief) that God can use Relics of saints as a means of conferring His grace. These where hankerchiefs and aprons sent to the sick by the Apostles (in this case they had been touched to the Apostle Paul).
At the time Acts was written crosses and crucifixes where not used, as crucifixion was a death penalty imposed only on the worst of criminals, and was seen as a more shameful way to die than even stoning. Early Chrisitan Iconography does not depict the crucifixion.