Ever wonder what technology is behind when you connect to the wifi system at malls, like SM or airports etc.? It is called Captive Portal. There’s quite a number of vendor out there selling their product but there are also linux based and free products. One that I can recommend is Zeroshell.
I’ve just installed one for my home network and it is really great. I am still in the process of digging deeper but as of writing, I’ve had a pleasant experience with it.
Other than captive portal, it can also be configured as a DHCP and DNS servers. It can also be used as VPN concentrator, when you want to connect to your home network from anywhere in the world. And, can also be configured as firewall and web proxy server.
If you are interested, google Zeroshell.org.