A device that makes it impossible for you to focus or think about anything. The more you try to think, the more the device shifts into a higher gear of distracting you. Basically a serious version of this.
To distract a person during an expected onset of phobias, panic attacks, unwanted intrusive thoughts.
The device would also be useful for self reprogramming. Upon doing/thinking something you don't want, at the click of a button you could give yourself a mini-punishment. In time you would stop doing whatever it was that triggered the punishment.
The battery powered device would have at its disposal :
several glue-on electrodes that you place on uncomfortable places (spine, tongue, gums, armpits, groin, neck, feet)
rapid heating/cooling pads (peltier elements) that you place on your kidneys and inside of tighs
earbuds for sudden screams, screeching noises, bursts of loud music
eyeglasses with strobing LEDs directed toward your eyelids
multiple glue-on poking devices that give you tiny pricks at uncomfortable places
a headband that periodically squeezes and releases, jolts, heats/cools
Ideally, all the gear could be placed on your body without it looking ridiculous. So a slap machine and various unusual looking additions might not be suitable.
The person should have an intensity dial mounted on their thumb so that they can easily tune the distractions up or down. The higher the setting, the more unpleasant it gets.
The device would put out random or coordinated impulses at varying speeds and intensity. It could range from intrestingly pleasant to please-let-it-stop.
Optionally, you could play a song loudly and have the device jolt, strobe, cool/heat, etc.. in the rythm of the music. Let's call it a "nightmare party mode" :)
You have to do something that is not dangerous but you have an irrational fear of it. You turn on the device for the time it takes you to get through the task.
You know that something will provoke your negative reaction. So you turn the device on and let the situation pass while you are incapacitated to react.