SwiftKey 4 is one of the best gesture keyboard apps ever. It is so good at predicting what you type, it borders on being creepy. I can rattle off e-mails, tweets and text messages to friends about sports, movies, tech, music – and based on what I’ve typed, SwiftKey occasionally finishes sentences word by word.

It does this by collecting data on what is typed as it's typed. The data is collected anonymously, feeding the app's learning algorithm to predict what you'll type next, based on what you've typed in the past. This means it does a scary-good job anticipating what you want to type. It’s not perfect, but it always offers suggestions, right above its keyboard. More often than not, I find those suggestions are spot-on. But the keyboard app’s prediction capabilities are just a part of the story.

SwiftKey 4, which officially hit Google Play on Wednesday, is a top-notch gesture keyboard app, replacing the stock keyboard on whatever version of Android you’re using. I’ve been using a beta version of the app for about three weeks and it’s among the first third-party keyboards I’ve actually enjoyed using.

My main handset is a Nexus 4. I use it daily and I’m a huge fan of its Android Jelly Bean keyboard, which has gesture typing built-in. On the Nexus 4’s stock keyboard, as you’re swiping along keys on-screen, Android does a solid job of predicting what word you’re typing. It’s so good in fact, that it makes going to an iPhone or iPad almost painful due to the lack of gesture typing in iOS. But SwiftKey 4 one-ups the Nexus’ keyboard by allowing you to type out entire sentences without having to lift your finger off the display between words.

As you're swiping across your phone’s display, SwiftKey guesses what you're typing. Those guesses change as you type more letters; when you see the word you want, just lift your finger. Or, keep swiping the letters of that word and then swipe down to the spacebar for a space, then start a new word – SwiftKey calls this feature Flow. If you’re not into gesture typing, simply type as normal. The app still throws out predictions.

Last year, SwiftKey’s app sat atop Google Play’s Top Paid Apps list for more than 20 weeks. It’s been installed by millions of people, and offers a keyboard for 60 different languages. Samsung used the company’s SDK to build SwiftKey Flow into the keyboard of its Galaxy S III and Note II smartphones, and its prediction technology is baked into the keyboards shipping on smartphones from a handful of Samsung's competitors as well. If you’re already using SwiftKey, the upgrade to the 4th generation of the app is free. Otherwise, SwiftKey 4 is a $3.99 download. It's not cheap, but it is worth it if you’ve got an Android and you're into gesture typing.