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.

2- Cellular shield SM5100B seems to have problems

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.

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