Does anyone know if there is a way to programmatically enable and read text in-app using the underlying Accessibility features available in iOS 5+?
To be clear, I am talking about the following feature (but of course doing this programmatically).

I am open to alternatives, but would prefer an Apple approved way to use this particular iOS 5 feature.
Unfortunately it’s not possible currently. The “Speak Selection” is only available to users that enable it in Accessibility settings and only for highlighted text in apps.
For programmatic Text-to-Speech you can check out iphone-tts. It works pretty well, though one caveat is that it only supports the voices it comes with, it doesn’t use the “Siri voice”. You can tweak the pitch and speed to your liking, but you won’t be able to match the built in voice for iOS.