For several months I've been looking for how to configure the Uc540 to accept iphones and how to configure the CISCOMOBILE App 8.1 (or the new Jabber) to connect to the uc540.
Before, some people write that its not supported yet, but yesterday I noted that even in the cisco uc500 site, the presenter in the video, Mr Mike Allen from Cisco, says at the end of the video that its supported with a new version of cme, any help or orintation its welcomed.
http://www.cisco.com/cisco/web/solutions/small_business/products/voice_conferencing/uc_500_series/index.html