I think you are focusing too heavily on on the concept of escrow. This is not something that requires a 3rd party and is not an escrow. Please, go back an read my post a few more times to let the concept sink in. This is simply a mechanism that protects the sender from sending the wrong type of currency, incorrect amount, or incorrect address used. It is a simple hold placed on the pending transfer. That is it. details of the pending transaction would show up in the deposit wallet. Think of it like a memo that sends 0.001 STEEM. It would send a memo to the deposit address and include details of the pending transaction.
In the future, STEEM will become something that you can use at starbucks, walmart, or the gas station. There needs to be a way for the sender to verify that he/she is sending the currency to the correct address, the amount is correct, and the type of currency (STEEM vs SBD) is correct. I can picture it now. The merchant would have a 2D barcode of their wallet address. I make a payment and start the handshake. There would be a screen that the merchant has set up that shows the memo. we can verify it manually or the merchant could have some simple software that verifies the transaction details.
You know, that system already exists with credit cards but is optional. Sometimes when you go to make the transaction, the details of the pending transaction are provided and you have the choice to continue. The handshake is inevitable. Eventually it will come whether you program it or someone else programs it. The question is if you are going to be the one that takes credit for creating it or will it be someone else?
I think such a feature does not need to be in the blockchain itself. Steemit.com has it, Steem keychain has it. And if you have a qr code, the company providing the qr knows it is correct and you can verify it with your frontend that asks for confirmation.
You have completely missed the point
Sounds like a confirmation mechanism.
What the handshake gives you is a blockchain proof of the seller confirming that the tx is well formed for whatever purpose that means. And I don't see much value in that so far.
But feel free to make a point as to why this is the next killer app.