Slowly but surely, Apple’s smart home platform continues to expand as more third-party manufacturers develop their own smart home gadgets with HomeKit support, and the latest such gadget may be the most useful one yet. Known as the Onelink, this $110 smart smoke detector is important because it compete directly with the Nest Protect, which was one of the first smart home gadgets to hit the market, and since it’s owned by Google, it hasn’t been bothered to make its devices compatible with Apple’s HomeKit.