When the Windows Phone 8.1 SDK leaked back in February, double-tap to wake was seen in the documentation, suggesting that Nokia's tech was being opened to all OEMs. Fast-forward to August and HTC's new One for Windows is the first non-Lumia Windows Phone to feature this useful technology.
Double-tap to wake came to Nokia Lumias in mid-2013. The optional tool lets users tap their display twice when it is off, letting people turn on their phones without using the power-button. Double-tap has always been a useful feature, especially if you only have one-hand available and you would like to use your phone.