Geeetech Iduino UNO R3 ATMEGA328P-PU Board+SIMCOM SIM900 Quad-band GSM GPRS Shield Development Board for Arduino/Iduino Quad-Band 850 / 900/ 1800 / 1900 MHz - would work on GSM networks in all countries across the world. GPRS multi-slot class 10/8;GPRS mobile station class B; Compliant to GSM phase 2/2+; Class 4 (2 W (AT) 850 / 900 MHz); Class 1 (1 W (AT) 1800 / 1900MHz); RTC supported.Selectable serial port.Speaker and Headphone jacks Low power consumption - 1.5mA(sleep mode)