StackSocial offers the BACtrack Vio Keychain Breathalyzer for iPhone and Android, model no. BT-M2, for $42.99 with free shipping. That's the lowest total price we could find by $7. It works with the BACtrack App for iPhone or Android to read one's blood alchohol content up to 0.400%. One AAA battery and three mouthpieces are included. Deal ends December 10.