Smartphones are electronic devices that are widely used in the current modern era. Ranging from children to adults are using smartphones. Lack of knowledge from smartphone users makes the use of smartphones improperly exceeding the body's limits. This makes a variety of negative impacts of using a smartphone. One way to overcome this problem is to use an electrocardiograph (ECG) sensor. The use ECG is to determine the fatigue of smartphone users based on heart rate rhythm. The sensor used as fatigue detection is the type AD8232. The result of this process is a secure or insecure condition for using a smartphone. When BPM is worth 60 <BPM <120, the condition of smartphone users is safe, whereas when BPM <60 or BPM> 120, the condition of smartphone users is unsafe. Based on the results that have been tested, the longer the use of a smartphone, the value of the BPM will sharply be reduced.

Wireless Sensor Network (WSN) is likely to be implemented as a long-range transmission network for sensor data to detect potential natural disaster like flood, landslide, and soil liquefaction. The sensor parameters: for example rainfall, soil humidity, vibration, type of soil, and so forth were sent from the location at which natural disaster potentially occurs and were forwarded to data center in real time for further analysis and observation. Therefore, the natural disaster which potentially occurs in the area was easily detected by the parameter of nodes that were gathered in server. When sensor detected the sign of natural disaster, the information would be conveyed through WSN to information center and was broadcasted to society as an early warning of natural disaster such as flood, landslide, soil liquefaction, etc. Such information was automatically broadcasted to society and was adjusted to the impending circumstance e.g. secure, cautious, and warning. By the implementation of WSN technology as an early warning system, it is expected to information concerning natural disaster is broadcasted accurately and rapidly to society, hence society can take quick action and response to natural disaster.