This is pretty cool and I'm mulling over uses for it where I work but a quick note: I really hate when my browser history is mangled just by clicking tabs/buttons. I understand the nice value of being able to share the current URL at anytime to transfer state but I wonder if that would not be better served by a share button that generated the URL. It's not a huge deal as I imagine this is a one-stop-shop sort of website, no one that you inject in the middle of your browsing. For me I only noticed it when I tried to come back to HN and saw my history was full of mission-patch.com.
Anyways it looks really cool and I hope to find a use for it!