I forwarded the post on side-cars on to James McKenna, and this is his response.
>
>Anytime a parent and infant are within arms' reach  (what I call sensory
>access) there are potential benefits. I think those side cars are really
>neat and a good compromise since not all folks are aware of safety issues.
>The physiological effects are probably a bit different than bedsharing--but
>nevertheless--it is cosleeping. Simply, it is not bedsharing which is one
>form (of the many different types) of cosleeping. Also, it has never
>been demonstrated that bedsharing reduces SIDS rates. This must be
>pointed
>out and we must be accurate on this. It is true that Asian cultures who
>cosleep do have lower SIDS rates--and I think it is related. But it is
>appropriate to indicate that only room sharing (as oppossed to bedsharing)
>has ever been shown to reduce the chances of SIDS--in controlled studies.
>Yours Sincerely, Jim McKenna

Katherine A. Dettwyler, Ph.D.
Texas A&M University