I plan on using Linksys WRT54GL's for this project.
I first need the device to be in Client mode, where the Linksys use its wireless interface to connect to a wireless network and act as a bridge to one of the Linksys Ethernet ports. I think this is a mode that is already supported in OpenWRT. I haven't decided if the Linksys will be acting as a DHCP server running NAT or if it will act as a transparent bridge and pass the IP from the parent network. If this has an effect on your quote, please add text to let me know the additional fee for this service.
Edit: One additional feature. If you have ever used a Netgear AP, it has a feature where you can just type "configure" or something like that into the browser and it redirects you to the config of the router. I would like that feature as well. I think that can be accomplished with a DNS entry into the router.
The next piece is a custom web page for simple configuration. For example, this page could be located at 192.168.1.1/config. I need this page for inexperienced users since they would be intimidated by the standard GUI.
The web page should have a button to scan for available network SSID and provide a list. I would like the list to only display insecure connections (this is for public access Wi-Fi). The user should be able to highlight the desired network and select "connect". Once connected the page should show status and display the parent network's IP address information.
That is all I can think of right now. Please ask me any questions that will aid you in producing an accurate quote.