It's not hard to under or over-tighten a bolt when you are building a cabinet, let alone installing hardware into the human body. Luckily, some clever engineers came up with the idea of SmartBolts.
SmartBolts, designed for industrial and medical applications, feature a simple color-coded indicator on their tops: If they're red, the bolt is loose. If they're green, nice job, everything's locked down. And if they're black, you may over-tightened things a bit, Mr. Look How Strong I Am.
Each bolt also promise 20 years of durability (which actually seems a bit low for many applications) as SmartBolts use simple fluid compression to measure and produce the chromatic indication in real time. That means there are no moving parts, and we fucking hate moving parts. [SmartBolts via medgadget]