**1. Introduction**

Obesity is one of the most serious public health problems of the 21st century and it is a threat to people's lives [1]. Obesity is influenced by several factors. At a personal level, simple things such as eating alone or in the presence of other people can affect a person's food intakes. Moreover, nutritional habits are also important factors influencing children obesity and overweight. For instance, restrictive eating practices are associated with weight gain [2]. Furthermore, people that insist on excessively control their eating behaviors show less ability to self-regulate food and energy intake across meals.

Not only human factors affect people's behavior, there are also non-appropriate environments that impact on human beings at a social level. For instance, when people operate in contexts that offer larger than necessary food portions, that have a high availability of energy-dense foods, or strong influence for sedentary behaviors, living a healthy life becomes harder.

Several efforts have been conducted to prevent and delay the growth of this issue. Mobile devices, heart rate monitors, chest pins and other devices are used for lifestyle monitoring and self-control. Moreover, many interventions have been developed over the years to determine the proper way to promote healthy behaviors. Lau et al. described that when technological applications or devices are used for these purposes, the results are either as effective as other ways of intervention. The only exception is face to face interventions [3].

Many efforts have been put into using mobile technology to promote healthy behavior. External memory aids play an important role in supporting habit development; they are useful when they refer to the target behavior and the situation in which it needs to be executed. Even though the effectiveness and relevance of reminders decrease with time, reminders keep people engaged and help them to repeat the behavior, and in some cases, could support the start of the new habit, as the new behavior might develop faster than the decay of effectiveness of the reminder [4].

The effects of mobile-based notifications have been established in previous works. The amount of notifications received in a mobile phone is now unmanageable for users [5,6]. Therefore, we believe that combining mobile applications with pervasive computing through smart devices could have more impact in the people and enhance their user experience.

By smart devices we mean: instruments, equipment or machines that have their own computational capacity. These electronic devices are connected to a network and interact autonomously with other devices and users [7]. Moreover, smart devices also refer to devices that have properties of ubiquitous computing.

In this paper, we describe a smart device-based system that helps to promote healthy behaviors with the aim of preventing overweight and obesity in children. Moreover, we present findings and suggestions for future developments obtained during the implementation and evaluation processes. The system has been applied in two scenarios; the first one intended to support parents in having a healthy snack routine, based on a nutritionist suggestion; the second scenario to deal with the problem of forgetting the required equipment on sports days, through notification reminders in the form of visual cues at proper timing. Both scenarios are focused on families with children between the ages 6 and 12, since it is important to take care of obesity in the early ages of the child as a strategy to promote healthy life, when physiology is more malleable [8]. Furthermore, the effects of the implemented actions are likely to be long-lasting. The goal of the system is to help people to establish routines that lead to healthier habits. Additionally, we want to use the proper technology and functionality to minimize user interaction and intrusion.

The system presented in this paper is developed in the context of a larger research with the goal of testing a conceptual framework to develop smart device-based notifications [9,10]. Moreover, the prototypes presented in this paper are developed using the knowledge gathered through the development of more than ten similar prototypes applied in four case studies.

The system uses different technologies including low cost microcontrollers, sensors and simple actuators to deliver information to the users, a NoSQL database to model people and devices into the system, and a lightweight messaging protocol to allow the devices to work with low processing capabilities consuming small amounts of energy.

The system was developed in the context of an international collaboration between Spain, Mexico and Costa Rica researchers. Moreover, the evaluation includes the perspectives of specialists in nutrition and physical activity from these three countries.
