Here are 2 apps to look at, one from each church. There are quite a few out there but these 2 appear to be better than most
Android
Prompter for Android.
https://play.google.com/store/apps/details?id=com.georgesdick.prompter&hl=en
Tablets have remarkable capabilities for video production, and one of the best uses teams a tablet up with mobile apps for use as a teleprompter. Now anyone can have clean, clear dialog using professional video tools.This free app from MonacoDevDroid has mirror mode, full screen mode, and can read plain text. You can add copy on the fly, directly in the prompter or copy and paste with ease. The app runs remotely using Bluetooth and has a built-in timer so you know how long your segment runs.
IOS
Teleprompt+ 3
https://itunes.apple.com/app/teleprompt+-3/id859980419?mt=8&ign-mpt=uo%3D6
Teleprompt+ 3 adds rich text support for inline formatting, a quick edit mode to make last-minute changes to displayed text without leaving the current session, and a new design for a Universal app that runs on both the iPad and iPhone. Because it’s an app Teleprompt+ takes advantage of iOS to enable features like remote control for multiple devices (have a technician adjust text and speed on a master device while text is displayed on a second iPhone or iPad), Dropbox import for text, and audio and video recording through the built-in microphone and cameras.