There probably is already a database for kumoricon registered users but allowing specific access to them would require someone to go through and categorize all of the people since there are different types of people that can access stuff, like the president vs a cosplayer.
Actually, I was thinking a registration database dump into MySQL. Then use Apache's .htaccess directives to control who has access to what screens.
Example:
/var/www/html/update/ This would be the folder where the various change/update pages are. Those pages would be used to update age, address, do they have parent form, etc.... Limited to the registration staff that can has update rights.
/var/www/html/register/ This would be where the new registration pages are run from. Only accessible by the people working the day-of sign up table.
/var/www/html/checkin/ This is where the general lookup to see if someone is registered would be at. All registration personnel can login to these pages. Much like the paper lists at previous cons.
This is all assuming that there isn't a good Drupal module for this. I have looked, but all of the Drupal modules for events are focused around presenters and back-end stuff, not registration/checkin of attendees. However, you never know, there might be something that can be used.
As for hardware, you would need either a laptop or desktop at each table, and then the server, which doesn't have to be much if you are only hosting a MySQL database and Apache web-server. My biggest concern would be connectivity. If wireless, how is it being setup to insure that no one else is getting on that segment. Not just for privacy reasons, but it would be pretty bad if a lot of people were hopping on the wireless and slowing the entire connection down enough that the registration people couldn't lookup information. If wired, then who is setting it up, where are the cables running, and is everything working before registration starts.
