TextExpander 3 is an update version of TextExpander that brings with it a custom keyboard for users running iOS 8 or higher. Not only can you store your snippets and use TextExpander as a place to store notes, you can now take your snippets iOS wide in any keyboard. Just set up your snippets in TextExpander 3 and then set the TextExpander keyboard as your default option.
For those not already familiar with TextExpander, the premise is that it helps you type a heck of a lot faster by letting you program snippets, or blocks of text, that you may have to type frequently. For many folks this can be email address, physical address, phone numbers, and even auto responses to emails. Just type out the full text once and then choose a keyboard shortcut that will trigger the snippet and it automatically expands the text for you.
Up until iOS 8, any snippets you have stored in TextExpander, you would have to access inside the TextExpander app by typing out your note and then copying and pasting everything. That's not the case anymore with TextExpander 3 if you choose to use the TextExpander custom keyboard as your default. Once enabled, you can type snippets that you've saved anywhere and they'll automatically expand, whether it's in iMessage, emails, Safari, or another app.
If you use Dropbox to sync your snippets in TextExpander across multiple devices, you can choose to link Dropbox to the TextExpander 3 app and all of the snippets you've already created will be readily available to you on iOS as well.