Employee Tracking System - Gig for Hire

I am looking to set up an employee tracking system when they come in and go. For my needs I want to employees to put an RFID chip through a 13 inch by 10.5 inch whole in a wall. They will get 1 credit if they stay in for 30 minutes. If they stay in for a period of time then they will rewarded with a "Super" title.

Obviously I want to do this using arduino. I have an Seeeduino Stalker - Water proof kit.
http://www.seeedstudio.com/depot/seeeduino-stalker-waterproof-solar-kit-p-911.html?cPath=84_13
This is my attempt to handle the data logging and communications.

There will need to be some way to track a quarter sized RFID chip through the 13 inch by 10.5 inch hole in a wall. I was thinking it could be done by making an antenna in a rectangular shape. Another path is to have a pad that can read about half way (6.5 inch) from the bottom. I don't know how to do the antenna nor the RFID chip. The RDID chip needs to be weather proof and some what abuse resistant.

I am willing to pay for your help. Please contact me for more information.

-Stephen

Check this out from Adafruit

Interested in hiring me and my 4 brothers as employees ?
We're very motivated since... your system would give each of us the possibility to earn the title 'super' in just 1/5th of the time. $)