Design Dilema -- What hardware?
Has anybody used an Arduino board to host an interactive web page, including user input via Submit / Form ?


I have a Tiny Web Server for the Arduino. It is designed to be light-weight on RAM. It supports GET/POST/Cookies for interacting with web forms.



Example code and more information on the linked page above.




  (Can I declare a local network static IP address for an Arduino?)


Yes.




  Other comments?


You could use NRF24L01 modules for short-range communication of wireless information. I have example code and schematics. My tests seemed to indicate 20m range was achievable.