The Global Keyboard Open Standard (GKOS) is an ongoing project to implement the full qwerty keyboard on a set of 6 keys. It is intended for use with tiny wireless terminals in order to minimize the space requirements. The standard was first published in 2000 and has been the subject of ongoing development. You can find a complete history on the project here. GKOS has evolved to include implementations for Android devices, the iPhone and other devices.