Nest Protect, an internet-connected smoke and carbon-dioxide alarm, is back on store shelves two months after a design flaw triggered a halt of sales.The problem was a feature called Nest Wave, which allowed homeowners to turn off the alarm temporarily by waving their arms in front of it. It was intended as a convenience — no standing on a chair and pulling out an alarm battery for scorched toast. But the company discovered the device could incorrectly interpret other nearby movements as a signal to shut off the alarm when homeowners didn’t mean to.Nest Labs, purchased earlier this year by Google for $3.2 billion, announced on April 3 that it was halting sales of the device as it looked for a software fix for the glitch. The company apologized for the problem and offered refunds. It also deactivated the feature remotely on all devices that were connected to the internet.The Consumer Products Safety Commission issued a recall for 440,000 of the devices on May 21 and instructed consumers to make sure their alarms got the electronic update via a wireless internet connection.Now the Protect is back on sale, for $99 instead of $129, and without the wave feature. The company will be able to reactivate the feature remotely should engineers find a fix.