With your Windows Phone you can unlock achievements and add them to your Gamerscore on Xbox LIVE. You can do this with the official Windows Phone Companion App. You can do much more with this app, such as hunting down your favourite movies, music and games. You can play everything you want and even launch and play them on your Xbox console direct from your Windows Phone.
If you add the Xbox LIVE Companion app with the Xbox LIVE Extras app you can unleash additional Xbox LIVE experiences on your Windows Phone by easily customizing your avatar on the go. You can also browse the marketplace for the latest avatar clothes and accessories to create the ultimate character. Remember that an Xbox LIVE Membership is required.