Today, Microsoft released the Lync Mobile client for Windows Phone, Iphone and IPad. ( Iphone and IPad not downloadable yet )
The deployment guide for on-premise users is published, but how do you get it to work with Office 365 Lync Online?
Well, it's really simple.
Just add the following 2 CNAME entries in DNS.
sip.domain.com, this should point to sipdir.online.lync.com.
lyncdiscover.domain.com, this should point to webdir.online.lync.com.
Replace "domain.com" with your own domain and it should work.
Make sure you wait until public DNS has replicated, if you test it right after the DNS change chances are that DNS is not updated yet and connection will fail.
Be patient :)
More information here : http://onlinehelp.microsoft.com/en-us/office365-enterprises/hh416761.aspx