Google Now already provides a ton of voice-activated functionality like sending messages or initiating calls, but a new app called Commandr aims to take that one step further. With it, you can toggle Wi-Fi, GPS, the camera LED light, and just about anything else you want through Tasker integration. This is done by turning Commandr into your default note-taking application, so when you initiate with "Ok Google" like usual and you say "note to self", you're actually issuing a command to Commandr.
Strictly speaking, the commands available natively are through Google Voice Search; Google Now just extends search to predictive results and cards based on your usage, and Commandr should work fine with Google Now disabled. Though Commandr's solution is a bit roundabout, and it can be tedious saying "note to self" every time you want to do something hands-free, of the options available this is the most painless. Plus, it's timely since the doors have recently been flung open to offer "Ok Google" triggers on every screen.
I've played around a little with this sort of stuff and it's possible to issue custom Google Now commands without doing a "note to self" beforehand, but you need root access, then get the Xposed framework with the Google Search API module installed, then install Tasker, then AutoVoice, then start programming in your commands. There's a run-down here if you're feeling adventurous.
If you'd rather not trudge through all that, hit up the Commandr app above and let us know what you think.