One problem I have with things like this is non-customizable hot words. For example, Google Now has this feature where it would always listen for "Ok Google" as

One problem I have with things like this is non-customizable hot words. For example, Google Now has this feature where it would always listen for "Ok Google" as long as your device is plugged in, which is a great feature. The problem is I have multiple devices, and saying "Ok Google" would wake all of them up, which is never what I wanted.