Making a Motion-Reactive LilyPad Patch

// LED lights up when the patch is moved or shaken.
// Accelerometer X/Y/Z on A2/A3/A4, LED on pin 5.

const int LED_PIN = 5;
const int X_PIN = A2;
const int Y_PIN = A3;
const int Z_PIN = A4;

int lastX, lastY, lastZ;
int moveThreshold = 60;   // raise to need a bigger shake, lower for a light touch

void setup() {
  pinMode(LED_PIN, OUTPUT);
  lastX = analogRead(X_PIN);
  lastY = analogRead(Y_PIN);
  lastZ = analogRead(Z_PIN);
}

void loop() {
  int x = analogRead(X_PIN);
  int y = analogRead(Y_PIN);
  int z = analogRead(Z_PIN);

  // total change since the last reading = how much it moved
  int movement = abs(x - lastX) + abs(y - lastY) + abs(z - lastZ);

  if (movement > moveThreshold) {
    digitalWrite(LED_PIN, HIGH);   // moving -> light on
  } else {
    digitalWrite(LED_PIN, LOW);
  }

  lastX = x; lastY = y; lastZ = z;
  delay(50);
}