SmartToolKit Alpha is a freeware application for Windows Mobile 5.0 based Smartphones that gives you one button access to a host of functions like cut, copy and paste while typing text in any application on your Smartphone using the limited keypad.(via)

Here are the features of this application:

-Press End-Key to bring the launch the application
-Clipboard Function like Copy, Cut, Paste, Undo, Redo, Select All and Clear All.
-2P ( Double Press ): New Innovative Function to boost your typing speed
-Navigate KeyPad - Remap the keypad to navigation key. Page Up, Page Down, Home, End, Delete, and Tab.

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