There's no shortage of options when it comes to customizing the iOS keyboard. Especially now that iOS 8 allows third-party keyboards, which can be downloaded in the App Store. iKeywi has been around for some time as a jailbreak tweak, and is now updated to iKeywi 3 for iOS 8 compatibility. The developer also launched an Apple-approved version of iKeywi on the App Store.
Both options, iKeywi (App Store, $0.99) and iKeywi 3 (Cydia, $1.99) provide similar features. The main difference is that jailbreakers don't have to fumble around with installing and using a third-party keyboard. iKeywi 3 simply becomes integrated into the stock keyboard when the tweak is enabled.