Sure, it's a neat-looking concept that Corbin Dunn came up with, as far as cycling death traps go. But in these economic times, it's also a practical solution for couples who'd rather not splurge on extravagances like a second wheel.
Unfortunately, Corbin forgot to save his "great post about the construction details", so you're on your own for now building a tandem unicycle for you and your sweetheart. I'm pretty sure that step one was "lose all rational sense of physical limitations" so feel free to get a head start on that until the full instruction list is up.
Update: Full instructions, if you've got sufficient wild abandon, can be found here.