I am trying to recompile all the information I can find in order to check if it is possible to do a really user-friendly SteemHalo which would work similar to BlackHalo.

If there are some Steem-Developers who are knowledgeable in this field I would love to get their input as well below this post for some questions:

• Is it possible to send outputs to a newly defined multisig-address which could have as a definition that the deposit amounts of both parties get refunded if the transaction is canceled by 2 parties (so that no new account for this operation would have to be created??)
• or if completed: the deposit amounts get refunded and the price is paid to the seller
• or if the maximum time for completion or cancellation is exceeded, the transaction is blocked forever.

This is the basic functionality of BlackHalo and does not need a third party. everything can be done by the buyer and the seller directly.

Instead of using BitMessage or an email, I guess one could use the Memo functionality of Steem?

Please, perhaps @xerox could provide some input if this is feasible and perhaps some code ideas/examples in order to get me or anyone else started.

Some links regarding this project:

http://blackhalo.info/
https://steemit.com/piston/@xeroc/piston-how-to-use-it-for-multisignature-accounts
https://github.com/steemit/steem-js/tree/master/doc#multisig

I think this would really be a great functionality that would set Steem apart from all other CryptoCurrencies