A simple Magento extension that allows to switch the currency by passing a GET parameter in the URL, for example: http://my-shop.com/product-xy?currency=usd.
Install using colinmollenhour/modman.
The controller_action_layout_load_before event, which is fired on every page load, is observed. The observer checks if a currency parameter has been passed with the current URL. If it has, it checks the currency code agains the list of allowed currency codes (with the getAvailableCurrencyCodes method), and if the currency code is in that list, the currency is switched by calling the setCurrentCurrencyCode method.
Most of my repositories posted here are projects created for customization requests for clients, so they probably aren't very well documented and the code isn't always 100% flexible. If you have a question or are confused about how something is supposed to work, feel free to get in touch and I'll try and help: [email protected].