TouchType is a simple little app that adds a lot of functionality to the iPhone. For $0.99, this app allows you to write out a message in landscape mode and easily insert what you've written directly into an email. While this app may have a short life ahead of it, for right now, it makes writing emails that much easier.
There isn't much to TouchType and there really doesn't need to be. When you load up the app, you can start writing in portrait mode, but there really isn't any reason for you to do this. Turn the iPhone sideways and then the app becomes useful. Whatever you write in this app is saved until you press clear, so if for some reason your long winded email doesn't save as a draft, you've still got a copy until you manually clear it.
Once you're done writing the email, just press the send button in the top right of the screen. This can be used two ways: for a new email or in a reply. If it's a new email, just make sure you don't have any messages open in your Mail app. If it's a reply, before you press send, make sure you've opened the email and pressed reply. Then just press the home button, load up TouchType, and press send. Now your message is inserted as a reply.
TouchType brings a functionality that Apple should have brought to the table a long time ago. Unfortunately, knowing Apple, we'll see this as one of their updates in the near future, killing the functionality of this app. But until then, TouchType is a must have app for anyone who uses their iPhone to write a lot of emails.