If you want to pull it out when you go to the dealership your best and easiest bet is going to be a MBC. Altough I favor the accuracy and reliability of an EBC, which is what I had in my car. I don't know of any with detachable faces per say, but you can always put it in an inconspicuous location...or just bite the bullet and realize that you are going to be modding your car and kiss that part of your warrenty good bye.