A wristband may be a good consumer product and you may be heading down a profitable path because people with bad habits (your potential end user) want help breaking their habit (or wants to show loved ones that they are trying to break bad habits).
In any case, I think it is easier to prevent the bad habit as early in the process as possible. That is, not when the wrist is making a cigarette-lighting gesture, but when the body starts walking away from the gas pump to buy the (cigarettes, potato chips, ice cream, beer, donut, lottery ticket) in the kiosk or convenience store next to the pump.