**1. Introduction**

Smartphones are similar to notebook computer with its own operating system, processor, internal memory, and high-quality camera lenses [1]. The smartphones are more accessible and cheaper than portable analytical devices. According to eMarketer, the number of smartphone

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

users worldwide surpassed 2 billion in 2016 and it represents more than a quarter of the global population. For 2018, the mobile users will grow to more than 2.56 billion people or a third of the world's population. However, the latest annual Mobility Report from Ericsson indicated that nowadays, there are 84 million new mobile subscriptions, reaching a total of 3.9 billion of smartphone subscriptions. Mobile subscriptions are growing at around 3 percent year-on-year globally. And it have been estimated that there will be a 6.8 billion of smartphone subscriptions for 2022. This growth has a big impact, and it highlights the opportunity to create apps and other services to meet our necessities in a practical way. The smartphone ownership rates in emerging and developing nations are rising, 21% in 2013 and 35% in 2015. **Figure 1** shows a distribution of the smartphone users by countries [2].

The continuous improvement of smartphone electronics, the development of new app and the increase of users have stimulated research in the use of smartphone. Smartphone technology now includes a range of detection capabilities, thanks to the built-in camera, such as colorimetric detection [3], optical methods that are employed in an easy way and to share the information on real time, as well as quantification [4], monitoring [5], or mobile applications [6–8] developed to solve a problem such as freezing of gait in Parkinson's disease [9], glucose monitor [10], and to detect enzymes [11, 12]. Also, it is used to developed devices, a

**Figure 1.** Smartphone's users in worldwide.

spectrophotometer [13, 14] and an electrocardiograph [15], and to create sensors or biosensors [1]. Some applications in healthcare, are: melanoma detection [16], cancer prevention [17], emergency signal detection [18], optical imaging techniques for diagnostics [19, 20], or detection [21]. Besides, in the environment, the smartphone has been used to analyze the quality of the water [22] to detect its salinity [23] or to detect mycotoxins [24, 25]. A complete revision of the applications in different area, devices developed, and limit of detection (LOD) of difference samples will be included in this review.

In this review has been illustrated the smartphone as a research tool to the detection and analysis, because these can be employed in interdisciplinary areas. One the most representative characteristics of the smartphone is that it allows the portability because of its size and its cost compared with commercials instruments. The smartphone sensors have the capacity to effectively serve as portable biofeedback devices for a diverse range of applications in science. Its processor allows you to collect, analyze, and process images or signals in an embedded way.
