I wonder how changing the perception actually impacts the body's thermostat. I would gladly sweat and let my body do its thing than have a heatstroke while being tricked into thinking that it is relatively cool outside.
Also as a result, you didn't notice when your body temperature was rising too high, so it did absolutely nothing to prevent heat stroke or any other forms of heat exhaustion. I'd be concerned about this wristband doing roughly the same thing.
It sounds great for my situation, though, where I'm sitting around programming in Costa Rica. I could turn off the A/C and let the house be its normal temperature of 85 degrees or so.
With cheap sensors, the room temperature, body temperature, humidity and perspiration can be measured.
Run some analysis and warning the wearer about heat stroke suddenly becomes possible!