Arduino is a development platform useful not only for amateur/hobbyist projects, but also for prototyping commercial solutions. Its modularity make easy the process of creating and evaluating concepts in a short space of time and with reduced costs. In this talk we are going to illustrate a development flow divided into three steps: the modular design, the prototype and the final product. The modular design intends to validate the main features of the product being developed, while the prototype has the goal of evaluating its performance. The two first steps allow us to validate the proposed product with reduced costs and reduceddevelopment time, as well as it helps reduce the need of making changes in the final product project in a later stage. To illustrate this process, we are going to go through the development of a GPS tracker with GSM communication made on top of open-source software and hardware. To present the development flow of a product prototyped with Arduino. To divide and detail its development cycle into three steps: the modular design, the actual prototype and the final product. To illustrate this process, we are going to go through the development of a GPS tracker with GSM communication made on top of open-source software and hardware.