I still agree it's the best approach.
That actually sounds awesome. You could reduce your interview evaluation overhead by nearly 50%!
Originally he'd simply asked if I could be there whilst he did the test so that he could talk aloud and bounce ideas off of me as it was timed and he gets nervous in tests and was afraid he'd not think clearly.
He froze. Totally.
I took over and did the test for him, and he aced it and was offered the job at the top salary band.
He is a perfectly good engineer and the company were very satisfied with their hire, but he never did that test. The test in it's entirety was completed by myself.
I cannot imagine this is such a rare thing with remote technical tests.
(Matasano is also not a company where it's easy to duck attention and coast; the tempo is 2-3 week engagements that wrap up with metrics that everyone cares deeply about).
The conclusion I draw is that cheating just isn't as big an issue as people think it is.