"Verbally is an easy-to-use, comprehensive Augmentative and Alternative Communication (AAC) app for the iPad. Verbally brings speech to those without and enables real conversation with its simple, intuitive design. Just tap in what you want to say and Verbally speaks for you. Premium Features available with an in-app purchase."

"Unlike other AAC solutions, Verbally's simple design allows users to communicate quickly and effectively, with very little physical effort. So intuitive, you can have a conversation immediately!
• Core Words Grid - contains 50 essential words to save you over 50% of the taps required to input your sentences.
• Core Phrases Grid - offers common phrases to enable faster & easier conversation.
• Text Prediction - learns the words you use and makes self-expression easier. Even import your contacts, to better predict names you use the most.
• Choice of 3 keyboard layouts or use a Bluetooth keyboard -just press Enter to Speak!
• Choice of male or female voice.
• Choice of settings for speaking method. Turn on “Speak Each Word” to have the app speak as soon as each word is completed or when you tap a phrase. Turn it off to speak after you’ve completed your sentence and tap “Speak”. You can also tap “Repeat” to say the last sentence again.
• A handy chime to get someone’s attention.
• Steady Hands feature – if you have limited fine motor abilities this feature makes it easier to type. With this set to “on”, the app will only register when you lift your finger off of the intended letter on the keyboard.
• No Wi-Fi or 3G connection required."

This is a free app, but there is also a Premium at a cost.