3 Smart end user devices
3.2 Smart watches

Smart watches are devices which provide similar functions like smartphones. In general, they are small computers in the form of a wristwatch or bracelet. They are able to work on their own or they can synchronise with a smartphone via Bluetooth and provide even more functions [17]. Except for Bluetooth interface they can be also equipped by wireless interfaces such as Wi-Fi, 3G, 4G, LTE, NFC and GPC. These allows them to communicate with external devices like sensors of various types (thermometer, heart rate meters/monitors, accelerometers, altimeters, barometers, pedometers, compass), speakers, headphones with microphone, head-up display devices, and of course with smartphones, tablets, etc. Some these sensors can be integrated inside smartwatches (e.g. GPS sensor, heart rate sensor). Smartwatches can collect data from internal as well as external sensors, process them and provide them with users in required form.

Fig. 9 Examples of modern smart watches

Besides the basic functions provided by standard watches such as actual time (and date), calculator, translations and games the smart watches offer functions as follows:

- telephoning,
- email, instant messaging,
- web browsing (even by voice commands),
- appointment schedule,
- various types of notifications (e.g. phone call notification),
- GPS positioning (e.g. during sport activities),
- payment in stores (virtual wallet),
- and many others.

Fig. 10 Overview of most often used functions on smart watches according to [18]

Smart watches often serve as a prolonged arm (screen) of smartphones because a lot of actions can be done without touching or even removing smartphone from a pocket. During synchronisation of smart watches with a mobile device compatibility is very important. There are watches which use own operating system (e.g. Pebble OS, Wear OS, Fitbit OS, Tizen OS) but they are able to cooperate with devices running Android OS or iOS. At the other hand there are watches (e.g. with watchOS or Android Wear) which are able to communicate only with devices running the same OS (e.g. from Apple).

Disadvantage of these devices is a low battery life (time). Many companies try to provide at least an innovative smart watch charging method. Except for standard charging via the USB interface there are available smart watches which can be charged wirelessly (e.g. Moto 360 watches from Motorola) or using an charging dock/cradle (e.g. G Watch R from LG). Nevertheless, low battery life still persists and in general it is valid that most of true smart watches hold for one or two days.

There are exceptions such as Vector Watch Luna, Garmin Vivoactive or TomTom Spark 3 Cardio + Music with battery lifetime higher than 20 days [19].

In Fig. 11 a general block diagram of smart watches is depicted. The smart watch heart is based on an application processor (with up to 4 cores and a frequency of 1 GHz) equipped by internal memory (e.g. RAM of 512 MB and Flash of 4 GB) that communicates with internal sensors and external sensors via a wireless (radio) transmitter/receiver and that depicts information on touchscreen (most often OLED, LCD, LCD e-paper) display with resolutions from 128x128 to 360x480. Smartwatches are usually powered by lithium-ion battery. Among 50 companies participated on research and development of smart watches we can mention e.g. Apple, LG, Sony, Pebble, Samsung, Motorola, Google.

Fig. 11 General block diagram of smart watches [20]