Mike says with the explosion of third party keyboards on the iPhone now, is there a security issue with it? Leo says that is a legitimate concern. However, Leo doesn't think it's really an issue. Apple does warn you though, that any keyboard can capture keystrokes and send them to the developer. Apple already does that. He recommends using SwiftKey. It will allow him to swipe letters instead of typing. It's more accurate and faster to type.
Mike says that he hears that Swiftkey saves the data. Leo says that nobody is making him use a different keyboard. So he should go with the one that he's comfortable with. If he's not comfortable with it, then don't use it. But SwiftKey uses that data only to make the keyboard more accurate by studying his typing style and they're getting no more data than his ISP or mobile phone carrier already gets. Any software is a black box for activity. So it comes down to whether or not he trusts the companies of the products he's using.
The one thing Leo is annoyed with though is that iOS 8 will switch back to the standard Apple keyboard randomly, leaving him to conclude that Apple implemented third party keyboards rather poorly.