diff --git a/src/dispatcher/iOSDevice.js b/src/dispatcher/iOSDevice.js
index a3dc5c0e2..1942e73f6 100644
--- a/src/dispatcher/iOSDevice.js
+++ b/src/dispatcher/iOSDevice.js
@@ -9,7 +9,10 @@ import type {ChildProcess} from 'child_process';
 import type {Store} from '../reducers/index.js';
 import type Logger from '../fb-stubs/Logger.js';
 
+import {promisify} from 'util';
 import child_process from 'child_process';
+const exec = promisify(child_process.exec);
+const execFile = promisify(child_process.execFile);
 import IOSDevice from '../devices/IOSDevice';
 
 type iOSSimulatorDevice = {|
@@ -22,33 +25,57 @@ type iOSSimulatorDevice = {|
 type IOSDeviceMap = {[id: string]: Array<iOSSimulatorDevice>};
 
 // start port forwarding server for real device connections
-const portForwarder: ChildProcess = child_process.exec(
+const portForwarder: ChildProcess = exec(
   'PortForwardingMacApp.app/Contents/MacOS/PortForwardingMacApp -portForward=8088 -multiplexChannelPort=8078',
 );
 window.addEventListener('beforeunload', () => {
   portForwarder.kill();
 });
 
-function querySimulatorDevices(): Promise<IOSDeviceMap> {
-  return new Promise((resolve, reject) => {
-    child_process.execFile(
-      'xcrun',
-      ['simctl', 'list', 'devices', '--json'],
-      {encoding: 'utf8'},
-      (err, stdout) => {
-        if (err) {
-          reject(err);
-        }
+function querySimulatorDevices(store: Store): Promise<IOSDeviceMap> {
+  const {connections} = store.getState();
 
-        try {
-          const {devices} = JSON.parse(stdout.toString());
-          resolve(devices);
-        } catch (err) {
-          reject(err);
+  return execFile('xcrun', ['simctl', 'list', 'devices', '--json'], {
+    encoding: 'utf8',
+  })
+    .then(({stdout}) => JSON.parse(stdout).devices)
+    .then((simulatorDevices: IOSDeviceMap) => {
+      const simulators: Array<iOSSimulatorDevice> = Object.values(
+        simulatorDevices,
+        // $FlowFixMe
+      ).reduce((acc, cv) => acc.concat(cv), []);
+
+      const currentDeviceIDs: Set<string> = new Set(
+        connections.devices
+          .filter(device => device instanceof IOSDevice)
+          .map(device => device.serial),
+      );
+
+      const deviceIDsToRemove = new Set();
+      simulators.forEach((simulator: iOSSimulatorDevice) => {
+        const isRunning =
+          simulator.state === 'Booted' &&
+          simulator.availability === '(available)';
+
+        if (isRunning && !currentDeviceIDs.has(simulator.udid)) {
+          // create device
+          store.dispatch({
+            type: 'REGISTER_DEVICE',
+            payload: new IOSDevice(simulator.udid, 'emulator', simulator.name),
+          });
+        } else if (!isRunning && currentDeviceIDs.has(simulator.udid)) {
+          deviceIDsToRemove.add(simulator.udid);
+          // delete device
         }
-      },
-    );
-  });
+      });
+
+      if (deviceIDsToRemove.size > 0) {
+        store.dispatch({
+          type: 'UNREGISTER_DEVICES',
+          payload: deviceIDsToRemove,
+        });
+      }
+    });
 }
 
 export default (store: Store, logger: Logger) => {
@@ -56,53 +83,14 @@ export default (store: Store, logger: Logger) => {
   if (process.platform !== 'darwin') {
     return;
   }
-  const simulatorUpdateInterval = setInterval(() => {
-    const {connections} = store.getState();
-    querySimulatorDevices()
-      .then((simulatorDevices: IOSDeviceMap) => {
-        const simulators: Array<iOSSimulatorDevice> = Object.values(
-          simulatorDevices,
-          // $FlowFixMe
-        ).reduce((acc, cv) => acc.concat(cv), []);
-
-        const currentDeviceIDs: Set<string> = new Set(
-          connections.devices
-            .filter(device => device instanceof IOSDevice)
-            .map(device => device.serial),
-        );
-
-        const deviceIDsToRemove = new Set();
-        simulators.forEach((simulator: iOSSimulatorDevice) => {
-          const isRunning =
-            simulator.state === 'Booted' &&
-            simulator.availability === '(available)';
-
-          if (isRunning && !currentDeviceIDs.has(simulator.udid)) {
-            // create device
-            store.dispatch({
-              type: 'REGISTER_DEVICE',
-              payload: new IOSDevice(
-                simulator.udid,
-                'emulator',
-                simulator.name,
-              ),
-            });
-          } else if (!isRunning && currentDeviceIDs.has(simulator.udid)) {
-            deviceIDsToRemove.add(simulator.udid);
-            // delete device
-          }
+  querySimulatorDevices(store)
+    .then(() => {
+      const simulatorUpdateInterval = setInterval(() => {
+        querySimulatorDevices(store).catch(err => {
+          console.error(err);
+          clearInterval(simulatorUpdateInterval);
         });
-
-        if (deviceIDsToRemove.size > 0) {
-          store.dispatch({
-            type: 'UNREGISTER_DEVICES',
-            payload: deviceIDsToRemove,
-          });
-        }
-      })
-      .catch(err => {
-        console.error(err);
-        clearInterval(simulatorUpdateInterval);
-      });
-  }, 3000);
+      }, 3000);
+    })
+    .catch(console.error);
 };