Philips Hue LED Light Bulbs
Amazon Echo first dipped its toes into smart-home waters by integrating directly with a select number of popular third-party gadgets. The most notable was the Philips Hue line of color-changing LED light bulbs. Sync them up with Amazon's smart speaker, and you'll be able to tell Alexa to turn them on and off, or dim them up and down.
Philips Hue White
You won't, however, be able to tell them to change colors (at least not yet). For that reason, syncing Alexa up with the white-light-only Philips Hue White bulbs might make more sense. And hey, they only cost $15 a piece.
Philips Hue isn't your only option for Echo-compatible lighting -- there's also Lifx, which makes color-changing LED bulbs with Wi-Fi smarts. Unlike Philips, Lifx offers a custom skill with extra controls -- including voice-activated color changes.
Stack's presence-sensing smart bulbs are another Alexa-ready lighting option.
Kuna's smart porch light is Alexa-compatible, and it's got a built-in camera, too.
iDevices also makes Alexa-compatible thermostats.
Emerson Sensi Thermostat
Of course, if you just want the cheapest Alexa-compatible smart thermostat, go with Sensi. It's pretty plain, but it'll get the job done.