http://y5wnzw4e6i7srm2gqadlow5anhlaj5avdkzbwzbmrxwkygxdp7ffieqd.onion/blog/noticer-noticing-ipv6.html
This seems like it can be used in a way for an ISP to be able to tell if there is a new internet device connected to the router (if Mr. Hacker Man accesses your router to do 'bad stuff' it will have his own IPv6 address which would hopefully aid you legally, somehow [probably not, gotta keep that conviction ratio up!].