Finger Keyboard is an application for Windows Mobile Professional (Pocket PC) devices that provides a replacement to the standard keyboards that are available as part of the operating system.
The application can be downloaded from the XDA Developers web site - http://forum.xda-developers.com/showthread.php?t=501122
NOTE - the application is available for a wide range of different display resolutions - be sure to download the correct installation package for your device.
Once installed, the Finger Keyboard is added to the list of available keyboards within Settings --> Personal --> Input, as shown above.
There are a wide range of options available to further control the behaviour of the keyboard: