diff --git a/README.md b/README.md
index 2eabdd8..3c53ce0 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ The following Shelly devices are supported:
 * [Shelly 1](https://shelly.cloud/shelly1-open-source/)
 * [Shelly 1L](https://shelly.cloud/products/shelly-1l-single-wire-smart-home-automation-relay/)
 * [Shelly 1PM](https://shelly.cloud/shelly-1pm-wifi-smart-relay-home-automation/)
+* [Shelly 1AddOn](https://shop.shelly.cloud/temperature-sensor-addon-for-shelly-1-1pm-wifi-smart-home-automation)
 * Shelly 2
 * [Shelly 2.5](https://shelly.cloud/shelly-25-wifi-smart-relay-roller-shutter-home-automation/)
 * Shelly 2LED
diff --git a/lib/devices/shelly-1-addon.js b/lib/devices/shelly-1-addon.js
new file mode 100644
index 0000000..d8ffb74
--- /dev/null
+++ b/lib/devices/shelly-1-addon.js
@@ -0,0 +1,55 @@
+class Shelly1AddOn {
+  constructor(device) {
+    this.device = device
+  }
+
+  async setExternalSensorTemperatureUnit(fahrenheit) {
+    await this.device.request
+      .get(`${this.device.host}/settings`)
+      .query(
+        { ext_sensors_temperature_unit: fahrenheit ? 'F' : 'C' }
+      )
+  }
+
+  async setExternalTemperatureAct(index, overAct, underAct) {
+    await this.device.request
+      .get(`${this.device.host}/settings/ext_temperature/${index}`)
+      .query(
+        {
+          overtemp_act: overAct,
+          undertemp_act: underAct
+        })
+  }
+
+  async setExternalTemperatureThreshold(index, overtemp, undertemp) {
+    await this.device.request
+      .get(`${this.device.host}/settings/ext_temperature/${index}`)
+      .query(
+        {
+          overtemp_threshold_tC: overtemp,
+          undertemp_threshold_tC: undertemp
+        })
+  }
+
+  async setExternalHumidityAct(index, overAct, underAct) {
+    await this.device.request
+      .get(`${this.device.host}/settings/ext_humidity/${index}`)
+      .query(
+        {
+          overhum_act: overAct,
+          underhum_act: underAct
+        })
+  }
+
+  async setExternalHumidityThreshold(index, overhum, underhum) {
+    await this.device.request
+      .get(`${this.device.host}/settings/ext_humidity/${index}`)
+      .query(
+        {
+          overhum_threshold: overhum,
+          underhum_threshold: underhum
+        })
+  }
+}
+
+module.exports = Shelly1AddOn
diff --git a/lib/devices/shelly-1.js b/lib/devices/shelly-1.js
index 39f6634..7850de7 100644
--- a/lib/devices/shelly-1.js
+++ b/lib/devices/shelly-1.js
@@ -1,4 +1,5 @@
 const { Switch } = require('./base')
+const Shelly1AddOn = require('./shelly-1-addon')
 
 class Shelly1 extends Switch {
   constructor(id, host) {
@@ -17,6 +18,8 @@ class Shelly1 extends Switch {
     this._defineProperty('externalHumidity', [3103], null, Number)
 
     this._defineProperty('externalInput0', [3117], null, Number)
+
+    this.addon = new Shelly1AddOn(this)
   }
 }
 
diff --git a/package-lock.json b/package-lock.json
index 22f0185..eecebff 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2276,9 +2276,9 @@
       }
     },
     "node_modules/minimist": {
-      "version": "1.2.5",
-      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
-      "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
+      "version": "1.2.6",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.6.tgz",
+      "integrity": "sha512-Jsjnk4bw3YJqYzbdyBiNsPWHPfO++UGG749Cxs6peCu5Xg4nrena6OVxOYxrQTqww0Jmwt+Ref8rggumkTLz9Q==",
       "dev": true
     },
     "node_modules/mocha": {
@@ -2786,7 +2786,7 @@
     },
     "node_modules/readable-stream": {
       "version": "2.3.6",
-      "resolved": "http://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
       "integrity": "sha512-tQtKA9WIAhBF3+VLAseyMqZeBjW0AHJoxOtYqSUZNJxauErmLbVm2FW1y+J/YA9dUrAC39ITejlZWhVIwawkKw==",
       "dev": true,
       "dependencies": {
@@ -5208,9 +5208,9 @@
       }
     },
     "minimist": {
-      "version": "1.2.5",
-      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
-      "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
+      "version": "1.2.6",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.6.tgz",
+      "integrity": "sha512-Jsjnk4bw3YJqYzbdyBiNsPWHPfO++UGG749Cxs6peCu5Xg4nrena6OVxOYxrQTqww0Jmwt+Ref8rggumkTLz9Q==",
       "dev": true
     },
     "mocha": {
@@ -5589,7 +5589,7 @@
     },
     "readable-stream": {
       "version": "2.3.6",
-      "resolved": "http://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
       "integrity": "sha512-tQtKA9WIAhBF3+VLAseyMqZeBjW0AHJoxOtYqSUZNJxauErmLbVm2FW1y+J/YA9dUrAC39ITejlZWhVIwawkKw==",
       "dev": true,
       "requires": {