by Knock, knock, who’s there? It’s your iPhone, unlocking your Mac! Knock is a clever solution pairing a paid iPhone app with free OS X host software, which allows owners of late-model Mac computers to log into their user accounts by simply “knocking” twice on the handset – even if it’s sitting locked and idle in your pocket.
The iPhone and iPod touch app performs this trickery by communicating with the Mac in question using the latest low-energy Bluetooth 4.0. In our tests, we noticed minimal impact to battery life throughout the day, but the downside is the software can only be used with newer Macs that support this specification. For MacBook Air or Mac mini owners, that means any model manufactured since 2011, while MacBook Pro and iMac computers need to be of more recent 2012 or 2013 vintage, respectively. That sadly eliminates an awful lot of potential customers, but the developer is quick to offer refunds for those unable to run the software.
Beyond initial setup, the app itself does nothing, at least until you decide to unlink it from a paired Mac. To get started, open both the iPhone and Mac apps, which initiates the Bluetooth pairing. Once that’s done, you must lock iPhone and then knock twice on the device to confirm that it’s working. Thankfully, this works equally well on the front or back of the device, relieving any fears of cracked displays from frequent knocking.
The OS X software adds its own login screen layer that matches whatever you’ve set up, but displays a green aura around your user image to confirm knocking input on the handset. Knock does exactly what it promises, with the somewhat large caveat that you’ll first need to wake the display before you start knocking – but to be fair, you also have to perform the same task before you can enter a password.
The bottom line. It may be little more than a high-tech parlor trick, but we quickly came to rely upon Knock after rarely bothering to lock a MacBook Pro with Retina Display, and we’re all the more safe for it.
(Editor’s Note: A previous version of this review incorrectly noted that the iPod touch is unsupported. The review has been updated to address that error.)
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