This is the tech part of a fitness tracker. If designed well it will be as efficient as a commercial fitness band. This piece of technology records the heartbeat and the number of steps of its wearer and displays it through an LCD display.

Step 1: Materials

Arduino board.
Wires.
Soldering iron and solder.
Resistor.
Pulse sensor for Arduino.
Force sensitive resistor Arduino.

Step 2: Introduction to the Sensors

Pulse Sensor (one with 3 pins):

Pulse Sensor is a plug-and-play heart-rate sensor for Arduino. It can be used by students, artists, makers, and developers who want live heart-rate data into their projects.

Force Sensitive Resistor:

FSRs are sensors that allow you to detect physical pressure, squeezing and weight. They are simple to use and low cost. FSR's are basically a resistor that changes its resistive value (in ohms Ω) depending on how much it's pressed.

Step 3: Setting It Up

The small block is the pulse sensor. It doesn't actually look like that but Fritzing didn't have one.

I have uploaded a picture of a heart rate sensor so that you know what it looks like.

This is the link to the GitHub page that will help you setup the pulse sensor.

Step 4: The Code

Add all the codes into a folder and open them on the same Arduino sketch but different tabs.

This should give you raw data on the 115200 on the Serial Monitor. This data will represent the number of steps taken by a person and that person's heart rate. This data could be used for various purposes.

Step 5: Adding the LCD Display

This is the Fritzing document for wiring the LCD display along with the rest of the fitness tracker. The code to the display is also linked above.

LCD (liquid crystal display) is the technology used for displays in notebook and other smaller computers. Like light-emitting diode (LED) and gas-plasma technologies, LCDs allow displays to be much thinner than cathode ray tube (CRT) technology.

A few points to note:

The code output is a quantity called signal. This increases with the rise in heart rate and decreases with a drop. The Pulse Sensor allows you to output BPM as well. To do this change the Signal in the lcd.print(Signal); to lcd.print(BPM); on the PulsesensorAmped_Arduino_Speaker tab.
I would recommend wiring the LCD display first and then the pressure pad and pulse sensor.

Step 6: Next Steps

All these components can be used with a smaller microcontroller and parts to make your own fitness tracker.

The one I have made with the Arduino is bulky and unattractive but with the knowledge about the sensors used in this project you can apply the same concept to a smaller microcontroller with smaller sensors and build you own fitness tracker.