An intraoral behavior monitoring and aversion device to assist a user in quitting an undesirable behavior such as tobacco smoking, tobacco chewing, use of snuff, illicit drug use, excessive alcohol consumption, excessive food consumption, and/or other undesirable activity facilitated via the mouth. The aversion device may be wholly or partially configured to be disposed in the user's mouth, for example. The aversion device may include a detector and a output device, wherein the detector is configured to detect a parameter indicative of the user engaging in the habit or undesirable activity. If (and only if) the detector detects such a parameter, the output device may, optionally, deliver a negative stimulus to the user, thus providing negative feedback and creating an incentive for the user to limit if not eliminate the undesirable activity. The device may be configured to store and/or relay data representing sensed conditions in the mouth.