Poly-Control's $179/£125/AU$229 Danalock fits over most existing deadbolts to add Bluetooth and Z-Wave connectivity to your current lock mechanism.
While this less expensive option seemed to have potential at first glance, it wasn't that easy to use. In particular, its "knock to unlock" feature, which is supposed to let you knock gently on your phone to unlock your front door didn't work at all during our testing.
Yale hasn't released its new Linus Lock just yet (it's scheduled to be released some time in 2016), but this model has a couple of unique smart features.
For starters, there's no keyed entry -- just a keypad for manually locking and unlocking the door in person. The Linus Lock is also supposed to be the first third-party product outfitted with Google/Alphabet's Weave protocol, a communications layer designed to help different smart-home products talk to one another.