I don't think "smart property" or "smart assets" under our current
understanding and technological level can exist without third parties.
I don't understand exactly what you mean with a "third party". Obviously, there must be an "issuer" that has some form of control of the "property" that is represented. In my example of hosting contracts it would be the entity that is offering the "physical" access to the server in the datacenter via credentials (normally the hosting provider or a reseller). In the case of a car with an access code, it must be the entity that controls the access control system and can guarantee access to the owner of the access code.
So smart property tokens would have characteristics of an "IOU", like those traded on different platforms like Ethereum, Ripple, or NXT; or on the Bitcoin blockchain via Counterparty or OpenAssets (thanks @krishnaprmod for examples).
Maybe you are thinking of a "smart property without an (human) issuer" - here I agree that technology is far away from that. But "smart property with an issuer" would surely be useful, because they would enable "decentralized trading" of these assets and new forms of crowdfunding - I started this thread to see if there are already experiencies with that.
Right now the tech we have, I don't think that blockchain can help anymore than being an intermediate between a transaction whether it is buying or selling of something or allocation of properties or bonds. Blockchain can only help in building a trust between the two parties since their transaction will be visible to all and hence there will be no fraud. What you are saying is something to another level. Some encrypted key to be used to unlock physical properties or things directly using blockchain tech is not possible as for now. But can be a good idea to research upon in Internet of Things.
Are you sure that it's not possible?
A problem with access codes I can imagine is that every owner must have a new code based on a kind of seed, because if all owners that buy a smart property token in its "lifetime" had the same code, these codes would be rapidly known (and spread by hackers through the web). But digital signatures provide a means for that - only that the device that controls access must be connected to the blockchain network. That should be doable even with a Raspberry Pi or a similar device ...
I have seen lots of ICO happening based on smart property or Digital goods and token represents the value of assets past several month increasing real estate project and other projects are happening. Its really good move.
Can you give me some examples? I have only seen ICOs raising "money for a business", but no one directly tied to a physical property.