Chatcast is an interactive webcast that allows viewers to post questions. Remote viewers participate in the live event, their chat or Twitter messages arriving at the event venue in seconds where they are moderated by someone in your department before being relayed to the participants.  There is also an unmoderated option where everyone watching the Chatcast can see all comments.

Chatcast example

$100 per Chatcast.
Chatcast fees are in addition to webcast fees.
Customization is available for a fee.