Trash compactor, Arduino Mega1280 and GSM module recommendation

I’m just beginning a project using an Arduino Mega1280. It’ll control (standalone) a trash compactor and send information via SMS. There are two areas of development: control and communication. In the control part I don’t see any obstacles: 7 digital inputs and 7 digital outputs, 2 of them connected to relays to operate forward and reverse rotation of a motor. In the communication part I need help. I plan to send a SMS messages every hour through a GSM module. These are the options: 1- Arduino GPRS Quadband Module. Costly, but this shield looks good. http://www.cooking-hacks.com/index.php/shop/wireless/gsm-gprs/arduino-gprs-module.html

2- Cellular shield SM5100B seems to have problems http://www.sparkfun.com/products/9607

3- Arduino GSM SIEMENS TC35 SMS Wireless Module UART/232A - lot cheaper ($37.90!!!) but it brings lots of additional work like physical connection of RS232 with USB and programming the communication between the two. http://www.ebay.com/itm/Arduino-GSM-SIEMENS-TC35-SMS-Wireless-Module-UART-232-/260842341023

Please, share any experiences or thoughts you have. Most likely it’ll save me some white hair. Thanks!