Welcome to SwitchPi website! We are concentrate on bringing the Raspberry Pi to Asterisk VoIP communication world.
We are producing two modules, they are PiTDM and PiGSM.
The PiTDM provides a module which can support up to 4 FXS or FXO modules.
The PiGSM provides a module which can support a quad-band GSM/GPRS, that is integrated a SIM800L module, that works on frequencies GSM850MHz, EGSM900MHz, DCS1800MHz and PCS1900MHz. That features GPRS multi-slot class 12/ class 10 (optional) and supports the GPRS coding schemes CS-1, CS-2, CS-3, and CS-4.
You can find out the details of both modules in here.