main.js

import { Component } from '@angular/core';
import { DeviceMotion, AccelerationData } from 'ionic-native';

import { NavController, Platform } from 'ionic-angular';

Array['max'] = (array) => Math.max.apply(Math, array);
Array['min'] = (array) => Math.min.apply(Math, array);

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  acceleration;
  x;
  y;
  z;
  heights = [];
  maxHeight;
  minHeight;
  subscription = null;
  totalPushups = 0;

  constructor(public navCtrl: NavController, private platform: Platform) {

  }

  ionViewDidLoad() {
  }

  calibrate() {
    // Watch device acceleration
    let initialHeight = 0;

    this.subscription = DeviceMotion.watchAcceleration({
      frequency: 1000
    }).subscribe((acceleration: AccelerationData) => {
      this.z = acceleration.z;

      if (!initialHeight) initialHeight = acceleration.z;

      if (Math.floor(initialHeight) !== Math.floor(acceleration.z))
      this.heights.push(Math.floor(acceleration.z));
    });
  }

  stop() {
    this.maxHeight = Array['max'](this.heights);
    this.minHeight = Array['min'](this.heights);
    this.subscription.unsubscribe();
  }

  start() {
    let up = 0;
    let down = 0;
    this.totalPushups = 0;
    let heights = [Math.floor(this.minHeight)];

    this.subscription = DeviceMotion.watchAcceleration({
      frequency: 1000
    }).subscribe((acceleration: AccelerationData) => {
      this.z = acceleration.z;



      console.log(Math.floor(heights[heights.length - 1]) - Math.floor(acceleration.z));
      if ((Math.floor(heights[heights.length - 1]) - Math.floor(acceleration.z)) > 2) {
        if (this.minHeight < Math.floor(acceleration.z) < this.maxHeight) {
          const middleHeight = (this.maxHeight - this.minHeight) / 2;

          if (Math.floor(acceleration.z) > (this.minHeight + middleHeight)) {
            console.log('up')
            up++;
          } else {
            console.log('down')
            down++;
          }
        }
      }

      this.totalPushups = up + down;
      heights.push(acceleration.z);
    });
  }
}