I've this situation:
I currently live in UK, but i'm italian. I've also a girlfriend there ( ), and we call each other a lot via normal cell phones, wasting a lot of money. I know that there's a lot of other way to communicate free, but i could teach her Skype, but not to my parents (and they have free unlimited calls to my italian number).
So i'd like to take a huawei 3g modem, with voice calls enabled, plug to a RPi and put in my home in italy, so the cellphone is in italy and there's no roaming fees.
The RPi should act as a translator from/to a voip line, that ends to an app on my smartphone. so i can use my data plan (or WiFi) to make/receive call.
Now i think that all can be done using asterisk, but i'm really new to asterisk world so i've no idea where to start and if it's doable.
The other way I've seen is an heavily modified version of mumble. I would run murmur (or better umurmur) and mumble client on the Pi, and mumble on my phone. The changes that i-ve to make in both client and server are 1) send/receive SMS and 2)enable dialing a telephone numeber.
Do you think is doable? have u any hints?