When Duet Display appeared last year it was the only option to use iOS devices with Macs and PCs that could work over wired connections. This made it the only app of its kind that worked without annoying video lags as is common with wireless options.
Duet Display impressed me when I reviewed it after its release, and the new version working with the iPad Pro is just as good. It is productive to have a two-monitor setup when mobile, and the high resolution screen of the iPad Pro rivals desktop systems when connected to a laptop.
It doesn't just create a productive dual-screen computer, it brings touch operation to the Mac on the iPad screen.
I've been using the new version to connect the iPad Pro to the MacBook Air, and the duo is a workhorse. It's quite a feat to use two monitors in a hotel room while sacrificing nothing compared to the desktop system at home.
Duet Display can't wirelessly connect an iOS device to a PC or Mac, but with regular lags in streaming video back to the host system as is common with such setups it is not missed. Connecting the iOS device to the host using a standard Lightning cable does away with the lags.
Duet Display is available in the iTunes App Store for $15.99 which is expensive for an app. The utility provided makes it worth the high price and it is highly recommended.