There has to be something meeting planners can take from Tate Britain's Christmas tree. Not the tree, but this idea:
"Visitors are invited to interact with the tree by leaving digital presents (photos, movies, texts etc) via the Christmas tree’s bluetooth antenna. If your phone has bluetooth you can send a file to the tree, choose the send via bluetooth option on your phone and choose Christmas tree from the available devices. If you cannot connect to the tree you can send your file via email to email@example.com. The digital presents will be unwrapped at www.untitledfolder.org/christmastree on Christmas day."
I could see some enterprising planner (probably for a tech show) who sets up something that symbolizes the show or some aspect thereof, and plants a bluetooth antenna in it that people can send snaps and messages to, then show a selection of them at the beginning of general sessions, or even just on the Web site during and after the event. While I pity the poor person who would have to wade through them all, it could be a really fun and interactive way to get people engaged with the event.