Arduino and GSM currently powered by laptop

     Having gotten the code to work and the Arduino Uno and Seeed Studio GSM board synchronized, the goal for the final project is to first incorporate a pressure switch and then apply an external battery supply. Having bought a pressure switch with ranges from 0-2.2 lbs, I need to collaborate it so it recognizes the slightest amount of force (envelopes are light). After collaboration is complete I need to combine the code that I used to send text message from the computer, with code for the pressure switch. Once everything is working, I can play around with the different messages or phone numbers that the messages will be deliver to.
     My goal for the final project is to attach a pressure switch that will trigger the Arduino and send text messages through the Seeed Studio GSM shield. My number one goal is to create a properly working code. After completing the code I will attach an external battery using the usb cable ( USB> battery with USB port>Arduino board). If I have any time remaining, I plan on creating a casing for the whole assembly to create visual appeal and protect from elements. I am still deciding what materials could be used to create a casing for the project (Styrofoam?, Lego blocks?, wood?, plastic?).

Arduino and GSM board powered using battery

Final goal of project. Pressure switch, external battery power, and working GSM board.

3 Questions:

1.) Besides being able to notify the arrival of mail what are some other events that this project could notify me about?
2.) What are some suggestions for casing of the project ( What materials? Styrofoam, wood, Lego blocks, plastic?)
3.) What are some general concerns with this project?