Microsoft have created their very own web application for the iPhone and Android device, which allows them to test out the Windows Phone 7 operating system, without having to buy a Windows Phone device.
Microsoft have designed a demo app which allows you to test out Windows Phone 7 without having a WP7 device. You can access it on an iPhone/Android device via the browser. The demo is located at http://aka.ms/wpdemo. The demo allows you to test out basic features that Windows Phone includes, such as Messaging, Outlook, People and more.
The web app can also be installed onto the homescreen, which provides a full screen experience on an iPhone or Android device.
This is most probably another attempt in advertising the Windows Phone 7 OS, allowing those without a Windows Phone 7 device to experience the barebones of what it can be like to own one an actual WP7 device.
Source: EngadgetFurther reading: Microsoft, Windows Phone 7