Source: https://community.homey.app/t/a-script-to-check-sensor-last-update/63142/9

const INVALIDATE_AFTER = 86400;

const invalidatedDevices = [];
for (const device of Object.values(await Homey.devices.getDevices())) {
  if (! device.capabilitiesObj) continue;
  let count = 0;
  for (const capabilityObj of Object.values(device.capabilitiesObj)) {
    if (! capabilityObj.lastUpdated || (Date.now() - new Date(capabilityObj.lastUpdated) > INVALIDATE_AFTER * 1000)) {
      count++;
    }
  }
  if (count && count === Object.keys(device.capabilitiesObj).length) {
    invalidatedDevices.push(device.name);
  }
}
await tag('InvalidatedDevices', invalidatedDevices.join(', '));
return invalidatedDevices.length != 0;

// Sensor.Check, to check on sensor last update time. Argument: inactive time (in seconds):

const INVALIDATE_AFTER = (args[0]); // Example 86400sec./3600 = 24hrs

const invalidatedDevices = [];
for (const device of Object.values(await Homey.devices.getDevices())) {
  if (! device.capabilitiesObj) continue;
  let count = 0;
  for (const capabilityObj of Object.values(device.capabilitiesObj)) {
    
    if (device.capabilitiesObj.measure_temperature || device.capabilitiesObj.alarm_contact || device.capabilitiesObj.alarm_motion ) { 

      if (! capabilityObj?.lastUpdated || (Date.now() - new Date(capabilityObj?.lastUpdated) > INVALIDATE_AFTER * 1000)) {
        count++;
        }
    }
  }
  if (count && count === Object.keys(device.capabilitiesObj).length) {
    invalidatedDevices.push("- " + device.name + "\n   (zone: " + device.zoneName + ")" );
  }
}

// When there are matching sensors
if ( invalidatedDevices.length != 0 ) {
  // create / update HomeyScript variable
  await tag('InvalidatedDevices', invalidatedDevices.join('\n'));
  
  // Send Timeline notification
  Homey.flow.runFlowCardAction({
          uri: 'homey:manager:notifications',
          id: 'create_notification',
          args: {
            text: "\nDevices without updates for " + INVALIDATE_AFTER / 3600 + "hrs: \n" + invalidatedDevices.join('\n') + "\n\nflow Sensors Check"
          },
        });

  console.log("Devices without updates for " + INVALIDATE_AFTER / 3600 + "hrs: \n" + invalidatedDevices.join('\n'));
  return("Devices without updates for " + INVALIDATE_AFTER / 3600 + "hrs: \n" + invalidatedDevices.join('\n'));
}
  
// When there's no matching sensor
if ( invalidatedDevices.length == 0 ) {
  // Just report "None"
  // create / update HomeyScript variable
  await tag('InvalidatedDevices', 'None');
// Send Timeline notification
  Homey.flow.runFlowCardAction({
          uri: 'homey:manager:notifications',
          id: 'create_notification',
          args: {
            text: "\nDevices without updates for " + INVALIDATE_AFTER / 3600 + "hrs: None\n\nflow Sensors Check"
          },
        });

  console.log("Devices without updates for " + INVALIDATE_AFTER / 3600 + "hrs: None" );
  return invalidatedDevices.length != 0;
}

// Original script by Robert Klep