Piety is a virtue that may include religious devotion, spiritually, or a mixture of both. Piety is a humility and religiosity.
Acts 16:16-34 is about a jail guard who attempted to kill himself but got told by God to not harm himself for we are all here and how people accused the jews of stealing money and the whole kingdom beat them. How the lord told sirs how to be saved by believing in him and he would be saved from evil and that same night he was baptized and he rejoiced that he was now a believer in God. A slave girl who was possessed met the apostles. She would follow them and call out and have fun with them. After many days Paul called the demon to come out of her in the name of the lord. When she returned her owners realized she could no longer fortune tell and could no longer make them money. Then the owners said that the disciples were disturbing the city and had them stripped of their clothes and beaten with rods, then put them in the cells.
The baptism is a sign of piety in this reading. Also praying and listening to God is the sign of piety.
The slave girl was spiritually devoted and brought money to her owner and a great deal of money by fortune telling.
The jews were punished and accused of stealing money. They got stripped and beaten with rods and still had a great belief in God.
Paul had stopped the guard from killing himself because he could believe in God and he had so much more to live for.