The BSXinsight is a wearable lactate threshold sensor that keeps track of athletes' lactate levels and lets them know when they're pushing themselves too far and are in danger of cramping up or dropping from exhaustion.
Lactate is a substance the builds up in the bloodstream when we're performing vigorous physical activity. When lactate levels are too high, we hit a 'lactase threshold', at which point we're unable to produce the required energy.
The contraption consists of a calf cuff and electronic module which determines lactate levels in the muscle before sending the pertinent readings to the user's mobile device via Bluetooth.
BSX Athletics, the Texas-based company that created the BSXinsight, successfully ran a Kickstarter campaign to raise funds to bring the BSXinsight to market. If you're interested, you can place a preorder for $420 and can choose between Cycling, Running and Multisport models.