Callsign is a busy sign app that turns a folded iPhone Duo into a sign facing the room, and the sign changes on its own when your calendar says you are on a call. You do not press anything, because the sign goes up when a meeting starts and tells people you are free when it ends.
Callsign is available on the App Store as a free download. Callsign Pro and the sign packs are one-time purchases with no subscription, and any iPhone running iOS 27 can run the sign through StandBy.
Callsign shows its sign on the outer display
Fold the iPhone Duo into a tent and the sign faces the room on the outer display. Fold it to 90 degrees like a laptop and the sign stands on the top half, with the time left and your call controls on the bottom half.
On any other iPhone, you can stand the phone on your desk and put the sign up full screen. You can also charge it on its side in StandBy, where the sign runs as a widget and a Live Activity takes over while you are in a call.
Callsign is a busy sign app that follows your calendar
Any calendar event with a video link starts the busy sign. Fifteen minutes before the meeting ends the sign turns amber, and when it ends the sign shows a message that you are free to talk, along with who knocked while you were busy.
Callsign reads your calendar on your iPhone, and your events are not uploaded anywhere. You can use all your calendars at once with Callsign Pro.
Call controls from the phone
- With Callsign Pro and the optional Callsign for Mac app, you can mute, turn your camera off, raise your hand or leave the call from your phone
- The controls work with Zoom, Google Meet and Microsoft Teams
- In laptop mode the buttons sit on the flat half of the iPhone Duo, next to the keyboard
Callsign starts free with one sign
The free Classic sign is green when you are free and red when you are busy, with the time you will be back. Callsign Pro and the sign packs add the rest.
- Callsign Pro adds a countdown, a loading bar, a traffic light, neon and a pixel-art mountain sunset
- Sign packs add Breakout and Pong, which play out over your meeting
- Other pack signs include a bouncing DVD-style sign, a microwave that dings when you are free and a lava lamp
You can change the words, colors and fonts on any sign you own, or let Random pick a different sign for each call. The minimal versions of every sign draw thin lines on pure black, and a screen saver with a slow drift keeps the words from burning into the screen.
