I was thinking of writing a kind of modified DHCPv6 server, which would be MAC-address aware, so you could maintain a table of MAC addresses and assign IPv6 addresses to machines based on table-lookup. Similar to what the Firebrick 2x00 can do already, but with IPv6 instead of IPv4. I don't know if it's doable yet, it's still just a very vague idea.
I'd also like to try to develop a tunnelling device so my iPad could get onto the IPv6 Internet over 4G/3G.