A simple keyboard designed for Handheld devices. Designed to work on a 480x640 or 240x320 device resolution. Use a compact layout, derived from "Android Physical keyboard" layout (not qwerty)
Use C# 4.0 / WPF / WinAPI.
Use Win32 API to lost focus every time is gained and a button clicked, so that the previous focus is restored. Try to use also a Cli wrapper for the native part.
This Keyboard does not need to be integrated in an appication, it's a standalone version.