Churches and religious organisations will pay you a premium to help them build apps. They can have their hymns, bulletin, upcoming messages, etc on their apps, integrate their social media and blogs and even include in app forms for prayer requests and counselling bookings.
They can send devotionals and service reminders as push notifications to their members and can receive offerings, tithes and vows. They can sell their products via mobile commerce and upload their messages via text, video, podcast and even connect their live streaming.
(You can set this up in less than 30 minutes with 360 Apps and easily charge $500 - $3000 per church!)