Before installing Mobility Service and Autodiscover you need this update http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=11551

When you deploy the Microsoft Lync Server 2010 Mobility Service, users can use supported iPhone, iPad, Android, Windows Phone, or Nokia mobile devices to perform such activities as sending and receiving instant messages, viewing contacts, and viewing presence. In addition, mobile devices support some Enterprise Voice features, such as click to join a conference, Call via Work, single number reach, voice mail, and missed calls. By using Call via Work, users can maintain their work identity during a call, which means that the call recipient does not see the caller's mobile number, and the caller avoids incurring outbound calling charges. With single number reach, a user receives calls on a mobile phone that were dialed to their work number.
When you use the Microsoft Lync Server 2010 Autodiscover Service along with the Mobility Service, mobile devices can automatically locate the URLs for Lync Server Web Services and the new Mobility Service regardless of network location. It supports client connections using either HTTP or HTTPS.

Mobil service: http://www.microsoft.com/download/en/details.aspx?id=28356

Microsoft Lync Server 2010 Mobility Guide: http://www.microsoft.com/download/en/details.aspx?id=28355

Windows phone 7 client : http://windowsphone.com/s?appid=9ce93e51-5b35-e011-854c-00237de2db9e