Lan Voice and IM chat for mobile

I need a voice and IM chat application that will allow anyone using the application to chat to other users also using this application, but all of this only on the local network i.e. LAN. The application needs to have the following: - voice chat - IM chat - group voice chat - group IM chat - must work across all the major mobile platforms, i.e. Blackberry, iOS, Android - must work on the LAN, no need for internet access - channel selection (just like a walkie talkie) - private channel with password - be able to work in background or when device screen is off, ie. like when iOS goes to sleep This application is ideally intended to mimic two way radio communication, similar to how the personal FRS radios work. Voice chat is the main goal for the the applications. IM chat is secondary feature. I will not entertain anyone that has not read this posting properly. Please submit initial replies with the answer of the following question. What is the total of four plus four.