Since each retailer or person accepting alternative currencies will have their own ideas about acceptance, we should make it easy for people to specify that to the phone apps. Is it possible for a smart phone to read a QR code and have that change the app's settings?
For example, a store might want to accept silver at spot plus 5%. A customer comes in and they can scan the QR code in the store and it sets their app to "spot+5%" for all the coins and cards. When they check out, the app is all set with the currently accepted prices of the merchant.
We could have ready-made QR code graphics up on our sites, making it easy for stores to use. We could also make handy business cards with the codes on the back so anyone can use them.