WiFi Keyboard is android app which allows typing on your phone using your computer's browser.
It works as ordinary input method. You can use terminal or type SMS ... Use WiFi for low latency input. 3G may be blocked by some carriers. USB connection works best, but require some technical knowledge and connected cable.
Available on Play Store: https://play.google.com/store/apps/details?id=com.volosyukivan
Available on F-Droid Store: https://f-droid.org/repository/browse/?fdid=com.volosyukivan
There is also a related project in development which provides Windows/Mac native client implementation: https://github.com/dportabella/DesktopKeyboard2Android