On Air

A tiny macOS menu bar app that turns a Home Assistant switch on while you are in a call, and off when you are not. Point it at the switch controlling your neon "On Air" sign and forget about it.

It works like a thermostat. A sensor reads the room (is any microphone live), a small policy layer decides what should happen (automatic on/off, minus any manual override), and an actuator flips the switch (a Home Assistant REST call). The menu bar item is the thermostat's little display and dial.

Instead of trying to recognise Zoom, Teams, Meet and friends individually, the app watches one CoreAudio signal: kAudioDevicePropertyDeviceIsRunningSomewhere. That is the same signal behind the orange recording dot in the macOS menu bar, so any app that opens the mic trips it. Detection is therefore app-agnostic and needs no microphone permission, because it reads device state, not audio.

• macOS 14 (Sonoma) or later
• Xcode 15 or later
• XcodeGen: brew install xcodegen

make open          # generates the Xcode project and opens it

Then in Xcode:

1. Select the OnAir target, open Signing & Capabilities, and pick your team (or set DEVELOPMENT_TEAM in project.yml).
2. Build and run. A small microphone icon appears in the menu bar.
3. Open Settings from the menu and fill in your Home Assistant details (below).

To build a Release binary from the command line once signing is set:

make build

The generated .xcodeproj and Config/Info.plist are not committed. project.yml is the source of truth: run make generate (or xcodegen generate) to recreate them on a fresh clone.

Open Settings from the menu bar item and provide three things:

• Base URL: e.g. http://homeassistant.local:8123 or your HTTPS URL.
• Switch entity ID: e.g. switch.on_air_sign. Find it in Home Assistant under Settings > Devices & Services > Entities.
• Long-lived access token: create one from your Home Assistant profile page (Security tab, bottom of the page). See the REST API docs. The token is stored in your login Keychain, not in plain preferences.

The menu bar icon reflects state at a glance:

• mic.slash: off air, mic idle
• mic: mic is live but the sign is being held off (override or automation paused)
• dot.radiowaves.left.and.right: on air, sign is on

Menu items:

• Automatic: master switch for the whole automation.
• Turn sign off for this call: silence the sign for the current call only. It re-arms automatically once the call ends.
• Launch at login: registers the app via SMAppService. This works reliably only when the app is built and run as a proper bundle (drag it to /Applications), not from Xcode's build folder.

• Bluetooth mics are the weak spot. Some Bluetooth input devices report as never running for this property, so if you take calls on AirPods, test that setup first. Built-in and wired/USB mics are reliable.
• Any mic use trips it, not just calls: dictation, Voice Memos, a browser tab grabbing the mic. For an on-air sign that is usually the behaviour you want.
• Local HTTP is allowed via NSAllowsLocalNetworking in project.yml. If you front Home Assistant with HTTPS you can drop that key.

Pushing a tag like v0.2.0 triggers .github/workflows/release.yml, which builds an ad-hoc signed OnAir.zip, attaches it to a GitHub Release, and updates the on-air Cask in calini/homebrew-tap.

Install via Homebrew:

brew install calini/tap/on-air

Or download OnAir.zip from the releases page directly. Either way, ad-hoc signing needs no Apple Developer account, but it also isn't notarized, so Gatekeeper will flag it on first launch:

1. Unzip (or let brew install do it) and drag OnAir.app to /Applications.
2. Right-click (or Control-click) it and choose Open, then confirm in the dialog. This is only needed once — after that it launches normally. (Plain double-click will just say the developer cannot be verified, with no option to override.)

To build the same ad-hoc signed zip locally: make release.

If this ever needs to run on machines you don't control (or without the Gatekeeper prompt), the next step up is enrolling in the Apple Developer Program, getting a Developer ID Application certificate, and notarizing the build with notarytool before zipping — none of that is wired up yet.

project.yml              XcodeGen project definition (source of truth)
Makefile                 generate / open / build / release / clean
Config/Info.plist        generated by XcodeGen (gitignored)
.github/workflows/
  release.yml            builds and publishes a GitHub Release on tag push
Sources/
  OnAirApp.swift         app entry, Settings scene
  AppDelegate.swift      status item: left-click toggles, right-click menu
  SettingsView.swift     Home Assistant configuration form
  OnAirController.swift  policy: mic + automation + override -> sign state
  MicMonitor.swift       CoreAudio sensor (is any input running)
  HomeAssistant.swift    REST actuator
  KeychainToken.swift    token storage in the login Keychain

MIT. See LICENSE.