VoIp Speech to text solution in C#.Net?

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C#

C#4.0

Hello,
I would like ask your opinion about a software. Recently I have read about
a software which was written in C# .Net 4.0. It is a VoIP softphone and
it can forwards and receives calls and it has speech to text function. It means that it can record the telephone
conversation on the basis of keyword. And in addition it is possible to convert this voice record to text format.
And later you can search in the text on the basis of the given keywords. It works with VoIP-SIP-SDK.
This site you can find the source code of it: http://voip-sip-sdk.com/p_135-c-speech-to-text-voip.html
Please share your opinion, because I am considering to purchase this SDK and create a softphone like this.