The TextExpander for iPhone & iPad custom keyboard requires Allow Full Access to be turned on so that it can:
- expand snippets by sharing snippet data with the TextExpander app
- play sounds for key taps and snippet expansion
The keyboard maintains a small buffer of recent key taps for the purpose of matching a snippet abbreviation. The buffer clears after a limited number of key taps, and is never saved to a file or transmitted anywhere.
The keyboard does not require or use network access.
A lengthier explanation is here: http://smilesoftware.com/blog/entry/what-about-that-scary-full-access-warning