It is sometimes challenging in standups to associate the card to which the speaker is referring to the conversation - particularly for infrequent guests. A low tech solution that I recently implemented for my teams is to use a laser pointer as the token that gets passed around. As the speaker is referring to cards on the wall he/she is expected to point, using the laser, to the cards(s) in question.
An ancillary benefit to this approach is that it can be an early warning sign for scope creep when a team member has no card to reference. It can also be a warning that cards are languishing in the "in-play" section - if nobody is referring to those cards, they may not be getting the attention you desire.
They're pretty cheap too.... you can get a laser pointer for as little as $10.