It works over some VPN's but not all. We will look into why and try to resolve.
Yes, it works very well when we need to call eachother or share files with eachother in the office. At home, I mainly use it to share large pictures and videos with my wife as it is very fast.
Yes, different channels and group calling should be added. We could add a chat function in it aswell.
Even though it is based on your local wifi and the data never leaves your home/office network, we have still encrypted it by default so we can integrate online calling and file sharing in a secure manner and dont have to redo the whole security aspect again!