Very very simple access point for virtual geocache?? Is it possible?

I have a feeling after searching the forum, I know the answer to this question already but I'm wondering if it would be even feasible or worth pursuing to try to build a very very bare bones wifi web portal on an arduino platform?

The difficulty I see is even if I can get wifi to work and get a very simple web page to work on it, I would like it to be the sort of thing that would be easy for any user to log into. (I'm thinking for something geocaching that would literally be nothing more than signing a log book to say "I was here" sort of thing) To make it user-brain-dead, it would have to have some minimal type of DHCP to tell a user's device (phone/tablet/laptop) how to connect and give it some kind of address, and some sort of way to either captive-portal or otherwise direct anything port 80 to the sign-in page.

Another possibility might be a very bare-bones Android/IOS app that handled the connecting and handshaking to a simple arduino wifi interface (which would take a lot of the burdens off the 'host' side while not laying them on the user as the 'app' could handle the nasty stuff)

Has anyone every played with anything like this? I'll probably try going with some sort of bluetooth alternative, but a user-friendly web page or app interface would make it a lot more user friendly for non-tech-savvy caching types.