There have been a bunch of virtual keyboards launched for iOS 8 in the past couple of months, but a newly launched app called Slated can serve as both a keyboard and a translator for the iPhone and iPad.
Slated currently supports over 80 languages. You type, it offers a translation, and you choose whether or not that or your native lanvuage will be what you send. According to the app description:
Slated is a keyboard extension - it can replace your keyboard in other apps, letting you converse in another language. And just by simply copying any text in that language, you'll see it translated back into yours. So you can and a friend can both type in a foreign language--even if it's foreign to both of you! Works with SMS, iMessage, WeChat, KakaoTalk, Kik, WhatsApp, Line, Facebook Messenger, Viber, Skype, and your favorite messaging app. Or any app that uses text!
Normally the app costs $4.99 but for a limited time it is available for just $2.99 in iTunes. It's worth noting that it does have some limitations, including a lack of autocomplete and error correct, as well as being a traditional hunt-and-peck keyboard. There are a lot of options there for iPhone and iPad keyboards and it's good to see something like Slated join the party.