The self claimed "world’s smartest touch screen keyboard for Android" is on sale for $0.99. I bought this app three weeks ago for $3.99 and I love it. It can learn from you email, Google+, blogger and predict what you want to type next. It save me lots of typing time. I have used many different kind of keyboard. This definitely is the best English keyboard on Android.
However, this app is not for tablet. There is a separate app you need to buy for tablet. Currently the price is $3.99. Tablet version can split the keyboard like iPad.