I never really put much though into how companies develop accessories for the iPhone and iPod. A company called Cypress has unveiled a new iPhone development kit that allows companies to easily design hardware to go along with the iPhone.
The dev kit is called the PSoC Expansion Board Kit for iPhone & iPod Accessories. The kit is designed to make it easier to prototype accessories like speakers, docks, and automotive accessories for the iPhone and iPod.
The kit allows for two-way communication between the iPhone and the accessory and includes an LCD display and capacitive touch sensing controls. The LCD can be used to display track meta data and more for the user. The dev kit is available now for $249.