I was just checking out a new service called, Wiffiti. It allows you to create a screen (see below) that will pull in content from Twitter and Flickr with specific tags. You can also give people a phone number to text their message. Try it: Text @wif24744 + your message to phone number: 87884
You can even post from the web and as the owner, you can remove posts from the timeline.
This screen is pulling all Tweets and Flickr photos with the tags: #edtech, #educhat, and #pln
I can see this as a great way to broadcast non-linear backchannel posts during a conference.