What do you do with them? You can wear it for Halloween or everyday, if desired. It may be for the anime otaku seriously into their cosplay. For the furries out there, I'm not asking so don't tell me.
Now what would the simplified caitlinsdad version be? Well, getting into advanced monitoring and feedback of brainwaves might be kinda expensive(they are dumping at the toy mega-store those Star Wars force trainers - control the floating ball with your mind- now $60 from $100 or maybe gut an i-dog but then I don't think the gears are powerful enough) and building some raw circutry is way more than I want to do. Pulley and invisible strings is so ghetto(Not that there's anything wrong with that...). A joystick that controls some motors on a headband? I know, how about servos controlled by an Arduino? And how about using an accelerometer to determine tilt/movement/position of the head to trigger ear movement. Tilt sensor switches might be too basic. GPS gets complicated and compass magnetomometer only points North.
This gives me a project to use with my recently acquired Arduino(no, it did not fall off a truck...I have a receipt). Besides, Caitlin says I have to make this or sew her a custom sling/messenger book bag.
This instructable may be more of an Arduino primer than about the cat ears. Note that this is a prototype project and I am throwing it out at this stage in the spirit of Open Source. I know it can be improved a lot by others and with more time to tweak it.
Okay, they look like bunneh ears, kinda like a cat.
With one of the ear coverings on...