I don't know anyone who's done it (it's still a bit too expensive for me to give it a shot) but it appears to be a fairly standard saliva sample kit that you mail in.

Yes compared to HDD it's way too expensive to read. However tape backups are also cumbersome and time-consuming to use, but the fact that you can get extremely cheap bulk storage from them means lots of big companies still use them. So I could see it maybe being competitive there (eventually).