Simple implementation

• Setup OpenBSD with authpf authentication.
• Write a webbased login using RoR with Ruby net-ssh support
• Create temporary login tickets on the server that can be used by client users.

Hardware

• Ubiquiti
• RouterBoard - Supported in OpenBSD 4.7. See e.g. RB600A support mail
• Alix boards - Long time support by OpenBSD

References

• LessNetworks
• NovelHotspotSolutions
• authpf FAQ