Card Module which has been talked about is also called Smart Card Mini Driver.  The specification for the same is now available for download at http://www.microsoft.com/whdc/device/input/smartcard/sc-minidriver.mspx 

If you have comments about the specification, please let us know.  If you have requirements or suggestions for API, then you will need to send us a detailed use case (scenario) and possibly some data on how important is this for your deployment.