In many ways, the integrations are designed to turn Nest into a less sinister version of Proteus IV from Demon Seed. For instance, if you have Automatic hooked up to your car, then Nest will begin warming your home when you're getting close. If you have a set of LG's smart appliances and the smart thermostat spots you leaving the house, your refrigerator will drop into an energy-saving mode, and will warn you if you've left the oven on. If you've got the Withings Aura smart sleep sensor parked beneath your mattress, Nest will set the temperature for a comfortable night of sleep before you wake up.
It's not just Nest itself that companies want to work with either. If you've got a Nest Protect smoke alarm and Philips Hue bulbs in your house, then at the first sight of danger, you'll get a red alert-style light show to warn you. There are plenty more announcements from other manufacturers like Uni Key, Ooma and Lutron, but it looks as if this is one bandwagon that's getting more popular by the minute.