How about an p2p escrow ledger with a Point of Sale Passcode.
For example lets say I am on my way to Walmart.
1. I tell my altcoin client to reserve 20 coins for walmarts use with a time limit of 24 hours.
2. I then reserve the amount using walmarts public key to reserve the amount in my wallet.
3. the altcoin network will remove the coins from my wallet and put them in escrow.
4. the coins cannot be sent to anyone or spent by anyone who does not have walmarts private key.
5. I goto walmart and spend 10 coins.
6. Walmart altcoin client sees that there is a reserve amount of 20 coins with walmarts public key signature.
7. Walmart then receives 10 coins from the reserve and using its private key releases the rest of the coins back into my wallet freeing up the remaining 10 coins for me to spend.
This is just an idea on how to speed up transactions.
Let me know what you think.
You can also incorporate a passcode into step 2. that way if Walmart is part of a group of retailers sharing the same private key then I can keep a larger amount in p2p escrow for use with multiple retailers. the only retailers that could take money out would be those that I am present in with my passcode ready.
The system could also be used for e-bay and the postal delivery service:
1. a seller on e-bay want to sell you a mining rig for 100 altcoins
1. e-bay seller gives you his public key
2. You reserve into escrow 100 altcoins using the public keys of the e-bay seller, e-bay, and UPS delivery service. The altcoin client removes the 100 altcoins from your wallet and puts them into the cloud secured by the public keys of the e-bay seller, e-bay, and the UPS delivery service.
3. Upon completion of the sale ebay signs the transaction with their private key.
4. Upon delivery and inspection of the mining rig the UPS delivery man signs the transaction with his private key.
5. When all the transaction has been signed by all of the private keys (matching the public keys already incorporated into the transaction) the 100 altcoins are transferred to the e-bay seller.
anyone else have input?
[UPDATE] I created and announced a project post for this idea here:
https://bitcointalksearch.org/topic/annproject-p2p-escrow-coin-for-fast-point-of-sale-systems-pos-208393