1) No, you can't. Besides, am I really going to get to examine this tamper-evident lock on the front door of your decentralised-Airbnb rental before paying for it? Not a chance.
2) Locks could be connected to the Internet without any messy block chains getting in the way. It would really on trust, but you wouldn't need any nation-states behind it. (You can also rent locks without internet connectivity at all and without blockchains, so Slock.it is really a double layer of wasted complexity)
You'd still need to trust the manufacturer, and that an entity with significant (nation-state? Fortune 50?) resources hasn't successfully tampered with it, but that's a lot easier than trusting the average owner of a lock.