Android: TouchPal Wave is the latest beta for the TouchPal Keyboard (which we've mentioned before). Wave combines gesture typing and predictive text to let you type out entire sentences in the time you would spend typing words with other keyboards, all with fewer errors.
The video above does a good job at explaining how the new keyboard works. In practice, it's a little less smooth than the video makes it out to be, but it does work. TouchPal Wave learns the words you use and the things you most frequently say in order to improve its word prediction. Once it has a good idea, as soon as you hover over a letter, it'll suggest a word. If you like it, hold until it displays and then move on to the next letter in the next word to repeat the process. If you don't, just swipe through the rest of the word like normal.
Once you get good at it (and TouchPal understands you fully), you can type entire sentences in seconds. If you make a mistake or TouchPal inserts the wrong word, tapping on it brings up alternatives.
The TouchPal developers unveiled the beta at the XDA Developer Forums. Getting access is a little laboured though: You have to follow the developers on Twitter, retweet their promotional tweet, email them with your XDA ID and link to your tweet to say you've done so, and they'll send you a registration code to activate the app. Once you've done all of that, you'll be able to use the app, which is updated frequently based on the feedback from the XDA thread. Hit the link below to visit the thread and get started.
Next Generation of Ultra Gesture Keyboard: TouchPal Wave [XDA Developers Forum via XDA Developers Blog]