Luna Display, the utility that lets iPads act as a display and control a Mac via USB or Wi-Fi (disclosure: they’ve sponsored my podcasts in the past), released a new Mac-to-Mac mode Thursday that will let any Mac running Mountain Lion or later act as an external display for another Mac, using the same fast, low-latency infrastructure as the rest of Luna Display.
A few iMacs made between 2009 and 2014 support Target Display Mode, which does something similar, but this can allow other Macs with built-in displays—I’ve got a 2007 iMac just cooling its heels in my office running Mavericks—to be put to use. (I hooked mine up and it worked, but I think I’m over non-Retina displays….)
This feature also works with Retina Macs, which never got Target Display Mode—and I’ve heard some encouraging initial reports that it works pretty well. I’m not too surprised, since Luna Display’s image quality and latency has always been solid on my iPad. Existing users of Luna Display will find this feature enabled in a free software update; the Mac that is not acting as the external display will need the Luna Display hardware dongle and must be running El Capitan or Later.