What would be the mechanisms or applications needed to make this happen?
With tools currently in production, I imagine you could buy something from someone with your currency, and the seller would receive the same amount in their currency. The tool/application uses Lumens as a bridge/currency converter. i.e. USD-->LUMENS-->PESOS. The Lumens are the pipe/channel/conversion mechanism. In the example, you can replace "USD" & "PESOS" with any currency, or store of value (pigs?), set-up as an asset/trustine on the Stellar system.