Bangle2 need help with barometer app

Your code gave a whole bunch of errors on the console, like the drawIcons function being missing, accel not existing, and so on. If you fix those then it kindof works. I made some other small tweaks, so try this:

var center = {
  x: g.getWidth()/2,
  y: g.getHeight()/2,
};
var MIN = 0;
var MAX = 12;
var NUMBER_OF_VALUES = MAX - MIN;
var SCALE_TICK_STEP = 4;
var SCALE_VALUES_STEP = 2;
var NUMBER_OF_LABELS = NUMBER_OF_VALUES / SCALE_VALUES_STEP;
var NUMBER_OF_TICKS = NUMBER_OF_VALUES / SCALE_TICK_STEP;
var ZERO_OFFSET = (Math.PI / 4) * 3;
var SCALE_SPAN = (Math.PI / 2) * 3;
var TICK_LENGTH = 10;
var HAND_LENGTH = 45;
var HAND_WIDTH = 5;
var maxZ = -10000; // ensure we call for an update as soon as we have data
function generatePoly(radius, width, angle){
  var x = center.x + Math.cos(angle) * radius;
  var y = center.y + Math.sin(angle) * radius;
  var d = {
    x: width/2 * Math.cos(angle + Math.PI/2),
    y: width/2 * Math.sin(angle + Math.PI/2),
  };
  
  var poly = [center.x - d.x, center.y - d.y, center.x + d.x, center.y + d.y, x + d.x, y + d.y, x - d.x, y - d.y];
  
  return poly;
}
function drawHand(value){
  g.setColor(g.theme.fg2);
  
  g.setFontAlign(0,0);
  g.setFont("Vector",24);
  g.drawString(value.toFixed(2), center.x, center.y * 2 - 65, true);
  var angle = SCALE_SPAN / NUMBER_OF_VALUES * (value - MIN) + ZERO_OFFSET;
  g.fillPoly(generatePoly(HAND_LENGTH, HAND_WIDTH, angle), true);
  g.fillCircle(center.x ,center.y, 4);
}
function drawTicks(){
  g.setColor(g.theme.fg);
  for(let i= 0; i <= NUMBER_OF_TICKS; i++){
    var angle = (i * (SCALE_SPAN/NUMBER_OF_TICKS)) + ZERO_OFFSET;
    var tickWidth = i%5==0 ? 5 : 2;
    g.fillPoly(generatePoly(center.x, tickWidth, angle), true);
  }
  
  g.setColor(g.theme.bg);
  g.fillCircle(center.x,center.y,center.x - TICK_LENGTH);
}
function drawScaleLabels(){
  g.setColor(g.theme.fg);
  g.setFont("Vector",17);
  let label = MIN;
  for (let i=0;i <= NUMBER_OF_LABELS; i++){
    var angle = (i * (SCALE_SPAN/NUMBER_OF_LABELS)) + ZERO_OFFSET;
    var labelDimensions = g.stringMetrics(label);
    var LABEL_PADDING = 5;
    var radius = center.x - TICK_LENGTH - LABEL_PADDING;
    var x = center.x + Math.cos(angle) * radius;
    var y = center.y + Math.sin(angle) * radius;
    var visualX = x > center.x ? x - labelDimensions.width : x + labelDimensions.width > center.x ? x - (labelDimensions.width / 2) : x;
    var visualY = y >= center.y - labelDimensions.height / 2 ? y - labelDimensions.height / 2 : y;
    g.drawString(label, visualX, visualY);
    label += SCALE_VALUES_STEP;
  }
}
g.setBgColor(g.theme.bg);
g.clear();
drawTicks();
drawScaleLabels();

function accelHandler(accel) {
  if (accel.z > maxZ) {
    maxZ = accel.z;
    g.clear();
    drawTicks();
    drawScaleLabels();
    drawHand(maxZ*10); // x10 just to match the scale better
  }    
}
Bangle.setPollInterval(80);
Bangle.on('accel', accelHandler);