Is it possible to use the GPRS module for controlling one arduino via SMS? That arduino must also have the possibilty of wireless communication with another Arduino uno using xbee modules. The GPRS Arduino should receive commands of switching and send some information (digital input status) via SMS.
Arduino 1 + GPRS + Xbee (receive via SMS, transmit/receive via Xbee to/from Arduino 2)
Arduino 2 + Xbee (transmit/receive via Xbee to/from Arduino 1)