I came across this company called Luster and I figured it would be expensive but man oh man was it beyond what I thought. It's widely used for businesses. I looked through all the different things they offered and I saw hashtag printers. It's like the ONLY thing we could even afford off that list 
Either way, I think it's still another great way to keep things interactive and for guests to have a keepsake.
You would create a unique hashtag related to your event (wedding or otherwise). They take photos from their own phone or any other device. They would then upload it to their twitter/instagram with your hashtag and the hashtag printer instantly prints out a 2" x 3" of the photo they just uploaded. We're definitely going to do it for ours! The concept is pretty cool!
*FYI: They provide an operator who sets up, breaks down and stays on site! Also, there are additional travel fees for any locations outside of their local markets in NYC, L.A., Las Vegas, Phoenix, Chicago, San Francisco, London and Toronto.*
