The RFID UHF Toolkit is no longer available. However, there are two tools compatible with Workabout Pro 4 that provide the same essential functionality:
EMDK for .Net Toolkit provides developers with the tools necessary to create C# and VB.NET managed applications. These tools include class libraries, sample applications, and associated documentation. EMDK for .NET allows Microsoft® .NET Compact Framework developers to programmatically access the enterprise mobility features on the devices. This developer kit is designed for use with Visual Studio 2005 and Visual Studio 2008.
RFID Input Plug-In for Datawedge provides a way for Zebra devices to read RFID tags and transfer tag data to a foreground application through output plug-in. DataWedge RFID Input Plug-in uses RFID3 APIs to communicate with RFID radio.