Sometimes to create a project/interface and avoid to spend to much time about technical issues using existing element could be a nice way to prototype idea.

To create a simple computer interface an object like a keyboard could be perfect to hack.

You will create a simple interface with the computer but completely embed into a garment.

Useful link :
Another tutorial
http://www.arduino-tutorial.de/2010/06/keyboardhack/

Soft to remap the key of the keyboard
http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=ukelele

Emulator of arcade games
http://mamedev.org
http://www.freeroms.com/mame.htm

Ref :
Eight steps by kobakant

Keyboard to a typewriter machine
http://www.instructables.com/id/Hacking-a-USB-Keyboard/?ALLSTEPS
Mario Bros interface
https://vimeo.com/90229696

Examples of Hard and soft connections 

website for keyboard interaction :
http://www.patatap.com/