I mean people can already bump most locks, or break a window, or in your case just climb in the window...

No house is really secure, and I'm not going to spend my time trying to secure it against non-existent threats.

That's not to say I don't want security. The threat of someone finding a loophole and being able to enumerate and unlock all smart doors is very real. But I'm not going to care if someone can come up with a scheme where they megaphone their voice to unlock the door, then somehow prevent the notification going to my phone letting me know someone is home, avoiding or destroying the few security cameras we have, and avoiding being caught by someone else during all this ruckus. Especially when they could just break a window...

Well, if it was

"Alexa unlock the door."

"Ok, what is the passcode."

<Looks at smart watch>

"123456"

"Thanks, unlocking door."

Now that I think of it, as someone that has 3 different 2f tokens.. smart watch integration would actually be useful in general... If I had a smart watch.

A smartwatch as simple as a Pebble can run such an app already. For example, I authenticate with 2FA with e.g. Google & Facebook w/my Pebble.

The problem is that I don't want to use my voice for commanding that much. It has privacy implications. First, obviously there is data being transmitted to a US corporation such as Google or Amazon. Second, there is analog audio data being transmitted. For example, that TOTP token generally stays valid for 30 seconds. In this window, an attacker could open the door right after you entered. I live in an apartment, and anything I say in the hallway can be heard by other people living on the same level as me while they are within their house (yep, terrible design).

I do admit that in the privacy of your home such analog audio data works better than say in public via your smartphone. But then again, smartphone is a can of worms with more privacy implications such as screen easily being seen by bystanders and cameras (a smartwatch has the very same issue; Google Glass wouldn't!). For the phone, Google Home is an interface, and certainly not (yet) the primary interface. For Amazon Echo, Alexa is the interface.

Bottomline, we need to think of these disadvantages (share our thoughts about them), and understand when they're too big to be a valid use case.

That's all just going the long way around. Why not just have the door (or Alexa) be able to talk Bluetooth to the watch to verify that it's there?

I'd like to be personally involved in some transactions. I think this will be a major use case for smart watches and a major feature of home interfaces (phone, smartwatch, or whatever has the totp) in the future.