I've dabbled in smarthome stuff for nearly 20 years, starting way back with good old fashioned X10 and home based servers to allow (clunky) remote control. It was neat but never 100% reliable.
Now, I have a mix.
For switches, receptacles, and other various electrical plugin items I use
Wemo - I have about 10 or so units throughout the house that allows me to control everything from our front house lights, my pool deck flood lights, basement and garage lighting (which now turns on automatically via a Wemo motion sensor when we ride the bikes in), right down to the LED accent lighting on my pool deck....from anywhere, anytime, so long as I have internet access on my smartphone. It had growing pains when I first adopted the hardware about 2 years ago, but now it's almost rock solid...and the units are not terribly expensive - $30-$40 range. No cost after that, and the phone app is slick with a lot of configuration triggers and options based on various things. It has become the core of my home automation now and I'm looking forward to adding automation to my garage doors and such as soon as the price of the "Maker" unit drops a little.
For my thermostat, x2 Honeywell WiFi thermostat - hard to beat for the money, works well, simple. I don't like the learning nature of the Nest - our house is too unpredictable and it would be often heating/cooling for nothing based on incorrectly learned patterns.
For temperature sensing and reporting, I recently invested in
LaCrosse Alerts hardware - it consists of a base station that connects to your router via CAT5 and then various temperature sensors, including modules for pool/hottubs, of course regular old inside/outside, water leak detection units (to alert of basement flooding for example). Most of the temperature based units have 2 channels, the base unit (which records temperature and humidity levels), and a remote probe (included) which can monitor a different area - ie, outside...or a freezer, etc...so they are like 2-in-1. It's a slick setup and there's a smartphone app that allows you to monitor it all (and receive alerts, although that does cost a few bucks a year after the trial period) if any of the sensors go outside the ranges you set. Hardware was priced very attractively as well via Amazon.
For cameras, I have a good old fashioned Lorex 4 camera system with the cameras in various locations around the property. The base station is squirrelled away somewhere that it's not easily accessable, and yes, it's viewable anywhere via my smartphone.