Officially running in beta, the Windows Phone variant of the application takes advantage of the unique capabilities of Windows Phone devices. I especially love the live tile support that "pins" your taxi booking to your home screen once it is confirmed, giving you quick access to just that booking (rather than plough through the application).
Available for ad-hoc use with cash payment to the driver, companies and individuals with Addison Lee accounts will be able to use these via the application and have it integrated into their monthly billing. The Windows Phone team in the UK must be enjoying the application, as they've put together this nifty video showing the whole process.
More at Addison Lee, or you can find the app in the AAWP directory.