Null Input Method
A non visible soft keyboard (Input Method) intended to be used with hardware Bluetooth and USB keyboards when you do not want a Soft Keyboard that covers a lot of the screen.
Get it from Google Play
Note that this is a very simple app that has no other purpose than to hide the soft keyboard for devices where this is not hidden automatically when an external (physical keyboard is used). If you need more than that, like international layouts, voice input triggering, key repeat rate control and more then External Keyboard Helper is the app you are looking for.