Fast prototyping a circuit

We have a fully functional communication between Android and Arduino and now it's the time to build a real circuit. Our goal is to turn on and off an LED using the Android system and this problem is little and self-contained. However, at the beginning, we could be a little more ambitious and, instead of turning on an LED, we may want to turn on a light bulb in our bedroom. So why create such a simple project while we can make things a little more interesting? Because we are fast prototyping our project.

Fast prototyping is a group of techniques that we can use to create our working project as soon as possible. This is really helpful because we are removing many implementation details, such as the product design, keeping the focus only on the core of our project. In our case, we are removing all the problems related to turning on a light bulb, like the use of a transistor, a relay, and an external battery, and we're focusing on the creation of a light...