Hello I am building forms over and over in iPhone and iPad apps:
I don't know of anything that combines all those features, but I recently open-sourced my validation library PMValidation on github, which I used developing the iPhone app Imprints. PMValidation comes with many basic types suitable for validating forms, and in fact that's what I originally built it for.
Using the PMValidationManager class you can easily listen to UITextViews or UITextFields, and update whatever graphical widgets you want via notifications. It's very modular and easily extendable, should you have more unique needs. It's under the MIT license.