Yes. To call this result "unsurprising" would dignify it unduly.

Imagine a world in which Google Glass other speech activated devices are the norm. A virus like this could potentially spread from person to person as they passed each other in the street, without anyone knowing, if it exploited a bug in the speech recognition tech. It's not interesting if it relies on the other computer already being infected, but exploits in image/sound parsing are not uncommon and could be combined with this. Another cool hack would be a physical real-world shape/pattern which exploited the image recognition software in something like glass to take over the device.

It's an interesting idea I think, which will have more applications in the future than it does now as more computers start to be always on, listening and watching, but mostly because audio or video is not an infection vector we take seriously yet in the same way that we do network infection.

That's how it seems to me. But a well-hidden bit of malware won't have a problem turning on the mic for a few seconds on the hour every hour to listen for a handshake chirp or the like. It's a limitation, but far from an insurmountable one.

Not only that, but the listening application must have some kind of exploitable vulnerability.