Biosensor tattoo which warns the athlete you, before you "hit the wall"

Here is an interesting tattoo which warns athletes before they hit the wall: This Biosensor Knows When Your Body Will Quit Before You Do:

The sensor sticks onto your skin like a temporary tattoo and measures the amount of lactate that your body produces in its sweat. Unlike its better-known cousin lactic acid, which only forms during strenuous anaerobic exertion, lactate forms during both mild aerobic exercises and strenuous anaerobic variety. Once your body reaches a specific lactate threshold, it shuts down regardless of your steeled willpower, and you hit the proverbial wall. By measuring how long and how hard you work before your body quits, the sensor can help athletes train more effectively and keep soldiers on patrol from over-exerting themselves.
Here is the abstract of paper:

The present work describes the first example of real-time noninvasive lactate sensing in human perspiration during exercise events using a flexible printed temporary-transfer tattoo electrochemical biosensor that conforms to the wearer’s skin. The new skin-worn enzymatic biosensor exhibits chemical selectivity toward lactate with linearity up to 20 mM and demonstrates resiliency against continuous mechanical deformation expected from epidermal wear. The device was applied successfully to human subjects for real-time continuous monitoring of sweat lactate dynamics during prolonged cycling exercise. The resulting temporal lactate profiles reflect changes in the production of sweat lactate upon varying the exercise intensity. Such skin-worn metabolite biosensors could lead to useful insights into physical performance and overall physiological status, hence offering considerable promise for diverse sport, military, and biomedical applications.

Electrochemical Tattoo Biosensors for Real-Time Noninvasive Lactate Monitoring in Human Perspiration.

If this connects with a smartphone or Google Glass we are set.