The Smart Knob promises a smarter, more secure deadbolt lock that lets us issue time-limited unlock codes or give trusted visitors a way in. Thanks to some hands-on time here at Engadget Expand, we've learned that it's even more clever than we thought. The PIN-verified, phone-based code generation system cycles through a seemingly "infinite" range before it hands out a number; someone overstaying their welcome isn't likely to stumble across the new code by accident. And while some might be disappointed that there's no built-in Bluetooth or WiFi to get codes, that actually works to its advantage, according to the project's Clark Li and Merrick Macker. As Sma
