"cellphone" shield?

I have spent the whole weekend trying to get this running smoothly.
Now I need help.

I have a SM5100B on the Sparkfun Shield.

OK, but remember that the GSM module will draw more power than the USB port can supply. How does your setup deal with this? Is there a battery (lithium-polymer cell)? Or do you have an external power supply capable of supplying about 2Amps?