Help: Paging + Asterisk + Android + External GUI

Hi Asterisk users,

This is my first post here and I hope to be an active user, not just asking but also helping others.

This is my project:

I was asked to develop an paging/intercom solution to use with Android devices. The idea is to have 3 components, the Android phones, IP PBX Server and a graphic interface running on a tablet. This last component is where I have more doubts. The graphic interface is just a small application to select the paging groups in a simple way, basically buttons and radio/check boxes. For the Android phones, I was thinking to use a free softphone that supports paging. The best would be to develop my own softphone but the quotations I have for a SDK are out of my budget. For the server, the main option is Asterisk. All components will be at the same LAN.

According to this scenario, these are my questions:

  1. Could you please tell me if it is possible to do it with Asterisk? If so what flavor of Asterisk you recommend? I already have some HW based options I am considering.
  2. Is it true it is better to use multicast instead of having a stream per each Android phone? What is the number of streams to start thinking on multicast?
  3. For the graphic interface, is AMI the way to go? Is there another tool that allows me to create a graphic application to communicate with Asterisk?
  4. Are there commercial solutions out there that can help me to develop this project in a fast and easier way? I have some budget I can use.

Thanks in advance for your help