I have a customer who would like to use an MC55 as a soft phone in a WI-FI environment. I found 2 Windows Mobile compatible clients capable of doing this (URL's  inset below). Has anyone had  any success with these or similar products
http://www.btrans.com/software/product/voice-over-wifi-softphone/

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http://www.cisco.com/comm/applications/IPCApps/Docs/PPCBrochure.pdf

http://www.ipblue.com/