Is it possible to register an iPhone or Blackberry as an IP Phone on the CCME(Router) 2800 or 2900? Such that when I enter my office premises I should be able to get an extension number exclusively on my iPhone or blackberry via WIFI as we get on any other IP Phone and I should be able to call any desk phone in my office on their extention number and also reach out to PSTN via my Office PRI number.
What are the pre-requisites that I need to take care of? Is this really possible on 2811 or 2921 router which is acting as a CME?
While this is not supported by Cisco this doesn't mean that it won't work. I would suggest configuring this and testing within your environment for yourself for a while before placing in production. Anything can be implemented with the proper planning.
HTH, Please rate if so