The UC500 does not have a controller built-in so it can't perform WDS similar so what an autonomous access point can do. Not sure about the VPN question but the UC500 provides site to site VPN's and SSL or EZ-VPN access for endpoints.
Configure Multicast Paging on the Cisco IP Phone 7800 Series or 8800 Series Multiplatform Phone
The Cisco IP Phone 7800 and 8800 Series Multiplatform Phones provide voice communication over an Internet Protocol (IP) network...
Add Call Park on a Cisco 7800 or 8800 Series Multiplatform Phone Key Expansion Module
Call park allows the user of the phone to put an incoming call on hold so that the call can be retrieved on another phone. A call is park...