diff --git a/native/app.config.js b/native/app.config.js
--- a/native/app.config.js
+++ b/native/app.config.js
@@ -2,9 +2,25 @@
 
 import ip from 'internal-ip';
 
+// Finds this machine's hostname in the local network. This is useful for
+// debugging on a real device. The `COMM_DEV` environment variable must be set
+// or this function will return `null`. The `COMM_NAT_DEV_HOSTNAME` environment
+// variable can be used to override the autodetected hostname.
+function getDevHostname() {
+  const { COMM_DEV: isDev, COMM_NAT_DEV_HOSTNAME } = process.env;
+
+  if (!isDev) {
+    return null;
+  }
+  if (COMM_NAT_DEV_HOSTNAME) {
+    return COMM_NAT_DEV_HOSTNAME;
+  }
+  return ip.v4.sync();
+}
+
 export default {
   extra: {
     // developer machine's hostname in the local network
-    natDevHostname: ip.v4.sync(),
+    natDevHostname: getDevHostname(),
   },
 };
diff --git a/native/package.json b/native/package.json
--- a/native/package.json
+++ b/native/package.json
@@ -11,7 +11,7 @@
     "clean-ios": "rm -rf ios/Pods/",
     "clean-all": "yarn clean && rm -rf ~/Library/Developer/Xcode/DerivedData/Comm-*; cd android && (./gradlew clean || true)",
     "postinstall": "bash ./postinstall.sh",
-    "start": "yarn expo start --dev-client",
+    "start": "COMM_DEV=1 yarn expo start --dev-client",
     "dev": "yarn start",
     "test": "yarn jest",
     "logfirebase": "adb shell logcat | grep -E -i 'FIRMessagingModule|firebase'",