Is there an app for the iphone that you speak and it types what you say?

^^^

Yes. It's called Siri.

Its like some assistent app which may reply similiar to your. Some apps are like changing the voice and then reply like copy cat.

Yes, Siri will type what you speak to it.

Also, when you input text anywhere (if you have Siri) then a microphone button will be on the bottom left of the keyboard and you can type that which will start listening and let you say as much as you want and then convert it into text.

Other apps that do the same thing include the Google Search App and Dragon Dictation.