[Asterisk-Users] Connecting extern telephones,

[satchid]

Dear List members,
I have an asterisk box whereon 45 GXP-2000 telephones from Grandstream are
connected at my work. This works fine. 
Now I want to take 5 GXP-2000s to different homes on internet and want them
to be part of the same internal telephone system. One external GXP-2000 is
to be the night receptionist that should be able to transfer calls to any
other of our extentions internally or externally. 
Then also I have 20 WIFI Handsets (F1000 Utstarcom) that work well on the
local Wifi stations, but they have to work on free AP al over the world as
well as internally as part of the local telephone system. 

What are my options to get these working for me? How can I get them
communicating to each other.

I hope that I gave the needed information, Please ask for more if needed.

Willy.