Expatmobile is a micro-sized virtual PBX, in other words "phone station".
Its function is to connect your Multifon* account to desired another SIP account. It allows you to have a russian mobile line diverted to another (cellular) number located in another country without roaming/extra fees.
This app is an indespensable if you need to make outgoing calls: it transmits to Expatmobile-Server, where you previously set up your Multifon-line, which number this line (Multifon) has to call after the Expatmobile-Server receives a call from your actual device, received over another local SIP account.
* Multifon is a SIP-copy of a mobile phone line offered by Russian cellular network provider "Megafon".
P.S.: does somebody know a mobile provider over the world who has the same SIP lines as Multifon - please contact us, we will integrate this in our service.