Nest has introduced Nest Protect ($129), a smoke and carbon monoxide alarm. Like the company’s earlier Nest Thermostat, the alarm can be controlled using an iOS app. Nest Protect is able give an early warning to smoke or let users know when carbon monoxide levels are rising by lighting up yellow and speaking with a human voice. Nuisance alarms can be canceled out by waving an arm near Nest Protect, rather than touching a physical button. Nest…