Hey, i have had a couple of recruiters who have approached with this idea. Basically, the recruiter says, okay i give you a week or two for this task to be complete ( the call is basically 30 mins or so explaining the problem and getting to know the basics about me ) and then post the time alloted, a sync up to see how you have solved it and to explain the design or solution or something like that. Only a couple of times have i had this experience. There is no additional overhead on the recruiter apart from reviewing it post the time alloted.
It felt better, because the interview was more like a typical work like situation. In work too, we are assigned tasks, and we update the progress.
Maybe its a bit idealistic, but then we all like to dream about utopia, don't we :)