The project entailed a pneumatic cannon with valves controlled electronically. When the cannon electronics receive a certain message over Bluetooth, the appropriate barrel fires. On the other side, an Android app uses the phone's Bluetooth modem to send messages to the cannon. This approach allows the cannon to be fired from around a 30-foot range, line-of-sight.
Here is a brief video describing what we'll be making:
We started the project on a Friday night and finished the bulk of by Saturday night. We worked pretty much non-stop, and all had experience working on this kind of stuff. With that said, we'd recommend carving out a whole week if you're working on this by yourself. So now that you're enticed beyond your wildest imagination, let's get started.
Please remember to be safe while building and using this device. You are entirely responsible for what you do with this information.