I do automation all day at work. When I get home I don't want ANYTHING moving, lighting, or talking to me on its own!
Seriously though, make sure you are thinking about cyber security when you're doing this. Whether it's a would-be burglar or the next-door-neighbor's kid who wants to make your pipes freeze while you're gone on vacation, you could be opening yourself up to some potential problems with getting hacked. (We ARE all aware that WPA2 - the supposedly un-crackable wireless security - has been cracked right? Check your router's vendor's web site for the firmware patch.)
Some tips:
1) First and foremost use STRONG passwords. Use as many characters as your device will allow and make them all different. DO NOT use a "method" that anyone with half a brain can figure out. I recommend the use of KeePass (it's free) for storing all of your passwords (devices, bank accounts, etc). I only know 3 of my passwords. One to log in to my work computers, one to log in to my home computers, and my KeePass password. All the rest look like this: "5^uI&wi0q%9yyhi" There are KeePass apps for iPhone and Google devices too so you can always have your passwords with you.
2) Keep the firmware and Operating Systems on all of your devices up to date. (Make it a monthly check on your calendar to go through every device you own and verify it's running the latest and greatest version.) Usually new firmware is fixing a security hole. Hackers LOVE out-of-date firmware and Operating Systems. It's their bread-and-butter
2) Lock down your router. Better yet, install an improved 3rd party software on your router like dd-wrt and/or set up an old PC with 2 NICs as a firewall (Sophos lets you install their software free for home use). Keep a close eye on the network traffic that is coming into and leaving your home and block addresses that you don't recognize. If you don't know how, either learn how or find someone that knows how. If you wanna run with the big dogs you've gotta get off the porch.
Hooking everything in your life to your wireless network exposes you to hackers. An attacker that knows what they are doing could easily get on to your network via your Nest and the next thing you know be rummaging through your computer getting your bank account numbers.
While this may sound like the preachings of a tin-foil-hat guy, believe me it's not. Once you attend a couple of cyber-security classes and seminars (the kind that are NOT trying to sell you anything) and go to places like Cyphercon (a little gig in Milwaukee that I've attended) or Black Hat (a big gig that I WANT to attend) you realize how prevalent this is - and how EASY it is for people that know what they are doing to hack you. The tools available out there are mind-blowing the first time you see them.
The reality is that there is little you can do to prevent a dedicated, motivated individual from hacking you if they are specifically targeting YOU. In most cases though, this is like locking the doors on your house when you leave and having security cameras. It "keeps people honest" and deters the "casual" person looking for an easy target.
I've done #1 and #2 above (and I'm telling you, once you start using it, KeePass is life-changing - I'm talking "religious" life-changing). I'm working on #3.
"Hasn't happened to me" yet? No? Well, I once saw a squirrel run across the road 9 1/2 times too. I bet he was thinking the same thing on the 10th try.