I just finished installing two Nest Protect devices. They are from the same company that designs and manufactures the Nest Learning Thermostat and they feature smoke and carbon monoxide detectors. Interestingly, they also sport motion detectors.
Presently, the motion detectors are used for reading gestures whereby a false positive can be indicated so that the noisy alarm is cancelled. But it is interesting to think of the possibilities now that we effectively have four smart motion detectors in our house in addition to the ones wired to the security system (the two Nest Protect units and two Nest thermostats that are also equipped with motion sensors).
A thing I'm keen to have my Nest units do - and which can be done entirely via software - is for the house to "arm" itself when we leave it (as indicated by the absence of the smartphones we carry all the time). "Armed" is a state that follows some specific rules.. if motion is detected while the house is armed, I immediately get an alert on my phone. I can then see what triggered the alert and decide what to do. As a low tech option it could include calling the neighbour and have them check. Hi tech would be to start a webcam, and if I don't like what I see I could trigger the alarm sound in the house via the Protect units - and perhaps via the Sonos system too. There are plenty of options: It becomes a sort of If This Then That for the connected house.
Nest has hinted that it will be possible to have some of their devices work together with a house security system and that more will be published in 2014. That sounds like a natural step for Nest to take but I like the idea of using Nest's network of sensors as a complete parallel security system. For one thing, it provides redundancy. But it also strikes me as smarter. Just like the Nest smoke detector offers a pre-alarm warning when small quantities of smoke is detected, there could be a number of scenarios that don't quite call for the standard burglar alarm with high pitched alarm bells and the police being summoned as a standard response.
Smarter sensors and smart things on the network allow for smarter responses.