Magento, one of the leading "open source" eCommerce platforms, has launched Magento Store Mobile, which lets users preview their Magento Mobile Application in advance of purchasing a subscription. (Magento Mobile now provides a free iPhone previewer application, available in the Apple iTunes Store.)
The Magento Store Mobile app is a fully functional iPhone application that allows you to preview all aspects preview of the application including products and styling in preview mode. The only omission is checkout. Just install the Preview Application on an iPhone and point it to the installation of the Magento Mobile extension you want to preview.