Milo Sensors has produced a soft Bluetooth 4 based wristband which monitors blood alcohol level through perspiration. There is a disposable cartridge on the inside of the bracelet which can monitor alcohol for up to 12 hours.

The PROOF App allows for preset blood alcohol alerts which will cause the wristband to vibrate when reached. There is also a closed social network aspect so you can monitor your friends alcohol consumption.  I like the “Time to Sober” counter. The company is working on more non-invasive biosensors.