Although this trips a few ethical flags for me (should we be taking advantage of the deluded?) I kind of love it. It makes me wonder if there are other services atheists are particularly suited to offering to fundamentalists.
In many ways, this is not much different than insurance.
Miller was a date setter, but not an advocate of the traditional fundamentalist 'rapture'. He was waiting for the second coming which would have been very public and would have taken the righteous up to heaven before Armageddon/judgement.