I love iPhone app promo videos, I get sent a bunch of them every week (not all good) but this one actually got me to head straight to the app store to download it. It’s called Knocking, a new app that lets you instantly share live video from iPhone to iPhone no matter where you are. Be gentle, I think they are ironing out a few bugs with their content servers, but the concept is fantastic! They also have a photo sharing version. It’s also free for the first 50,000 downloads.