Coding an OS is out of the question, unless you have a team of pretty good developers a big budget and a lot of time.
Using Linux distros, MS embedded or MS normal OS is the path to go. Here is a bit info :
Here’s a list of some distros with kiosk mode support.
Porteus kiosk The mini distro Porteus has a dedicated mod to support kiosk mode. Provides options to customize as need on first boot. Instant WebKiosk Boots from USB key and browser only. Can Bike OS Puppy based live-CD OS with a web browser and little else. SanicKiosk Turn-key web kiosk designed for public libraries, city government, health clinics, and other institutions in need of public information stations. It is intended for easy installation and administration by users with minimal technical knowledge. Ubuntu Guest login Normal Ubuntu installation allows guest access from the login prompt. A perfect solution for kiosks. Login into guest mode with restricted permissions but non-restricted browser. Works from USB too. Scientific Linux 6 and CentOS 6 Both the distros can be configured into kiosk-mode automatically by running this script. Webconverger (Unconfigured edition) Runs from USB, easy management console, highly secure, privacy conscious & fool-proof. No vendor lock-in, malware-free & firewall included. The Unconfigured offering is perfectly usable and free of cost. justbrowsing A bootable Linux “Live CD” that does not make any changes to the existing operating system on the computer. You can use the browser of your choice. Bundled webapps include a calculator, text editor, timer and more. Settings can be saved to a USB drive.