At an event today in San Francisco, Nest announced that it is releasing a second-generation smoke detector, and it's also called the Nest Protect. The new detector has a "split spectrum sensor" for smoke detection, a step beyond the single photoelectric in the original one. Nest says that ability to detect smoke with a sensor that can read shorter wavelengths is important because modern building materials can burn much faster, so the sensor should be able to detect smoke more quickly. It also lets you silence the smoke alarm from the app on your phone. That makes sense, as the "wave to silence" feature on the first gen version ran into problems.

The hardware has been completely redesigned to be 11 percent smaller as well, Nest says. There's a new "smoke chamber" to keep dust and insects out of it and it's easier to install than the original version. Nest says that it costs $99, with preorders starting today and shipments beginning at the end of the month.

Nest says that the new Protect constantly tests itself, right on down to testing its own alarm. It has an embedded microphone that can listen to hear if the smoke alarm's beeps and alerts are working. Nest says it will do those tests when it think you're not home, so it doesn't annoy you.

In addition to the new hardware, Nest also announced software updates for for its existing products that'll make them work better together. For starters, the Nest Learning Thermostat is now smart enough to shut down if the Nest Protect smoke and carbon monoxide detector goes off — the thermostat will note on its screen that it has been disabled due to a smoke or carbon monoxide event, and you'll also get an alert on your phone.

There's also a new "safety temperature" feature — if your home gets too hot or cold, you'll get a notification that the heating or cooling system has gone into override mode and activated to get your house out of the danger zone. Nest gave the example of a house that was too hot for your pets or cold enough that pipes would burst. This update will roll out to all of Nest's thermostats and smoke detectors soon.

Lastly, Nest introduced a new partnership with insurance companies called Nest Safety Rewards. If you let your Nest Protect give your insurance company some basic info — the Protect is on and functioning with charged batteries, Wi-Fi active, and sensors working — you'll get up to a 5 percent discount on your home insurance. Liberty Mutual and American Family are the first insurance providers participating in this program, and they're giving participants a free Protect. In terms of privacy, Nest said that users could stop sharing their Protect status through the app at any time, and no personal information is ever shared with your insurance company.

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