iPad-as-secondary-display apps have been around almost as long as the iPad, but most who used them once have seldom used them since. These things mostly work over Wi-Fi, and work poorly over Wi-Fi at that, with unwatchable video performance, choppy animation and tons of lag, even in the best of circumstances. Duet, a new app from a team that includes ex-Apple display engineering talent, changes all of that with a secondary display experience on an iPad (or even an iPhone) that feels like magic.
I was initially highly sceptical of Duet founder Rahul Dewan’s claims regarding his app’s performance – lag free performance, even for games (on recent Macs) with 60fps refresh rates? Sounds like a “go home, you’re drunk” situation. But Duet manages it, and with minimal installation headaches, too.
The key to the magic is using a wired connection (via Lightning or 30-pin dock connector) and the mandatory installation of a new display driver on your Mac that will recognize the connected iPad as a monitor. This does require a restart, which if you’re like me and almost never do that, plus have thousands of things open, can be a bit annoying. But once you boot back up, Duet is installed as a menu bar application, and provides a helpful tooltip window at first launch to get you started.
On the iPad side, you simply purchase and install Duet from the App Store and then open it to get things going, then so long as you’re connected via cable to your Mac and the OS X application is already running, it should find your iPad and automatically add it as another display, just like those you’d connect via Thunderbolt, DisplayPort or HDMI. You can adjust frame rate and resolution according to your machine’s performance capabilities, and your battery conservation needs.
The issues that I found were minor – some strange artifacting appeared on one of my other external monitors, a remnant of a moved Finder window that disappeared when I brought my mouse cursor to the area; and high CPU usage, which didn’t otherwise appear to affect performance of apps including Final Cut on my office iMac, but which might affect battery life considerably when used with a notebook. Neither issue will prevent it from becoming a daily use utility, however.
Dewan told me he created the app based on a wish expressed by his father that he able to use his iPad in this manner, after which he battened the hatches and created Duet in an intense development cycle covering just 30 days – aided by his experience as a display engineer working at Apple on both the Mac and iPad side.
Duet works with only one iDevice at a time for now, but support for additional devices, as well as improved CPU usage and even Windows support are planned for the future. The app is $10 on the App Store for a limited time, and the companion app is free. If you’ve ever bought a secondary display app in the past, or wanted to but were scared off by questionable performance, you must get this one.