There are two projects that aim support smart cards. There is MUSCLE which is an acronym for Movement for the Use of Smart Cards in a Linux Environment and can be found at
http://www.musclecard.com/index.html. There is also OpenSC which can be found at
http://www.opensc-project.org/opensc. Both these projects could support smart card integration into solid.
The only property that's currently supported is the reader type (Card Reader or Crypto Token) as this was all Hal was going to provide.
One use case I see is KDM where you can logon by inserting your card and typing your pin. This would require additions to the interface such as:
bool SmartCardReader::isCardInserted() const;
signal SmartCardReader::cardInserted();
If you're feeling so bold I would be happy to help test with my reader (although I'll have to find my smartcard).
Chris