The Swiftkey app studies your messaging patterns in Gmail, Facebook and Twitter to anticipate what you're going to type next. Version 4 of the Android-only application, which claims more than 15 million downloads of previous releases, includes a heat-mapping function that determines what keys you tend to miss or tap poorly. "It really goes that bit further to understand you and help you type. ... It's constantly analyzing that to give you a better typing experience," Swiftkey's Joe Braidwood says.