The five point harness (on the Bob, you have to unscrew it) fits through holes in the back of the bag, so there's no safety issue. With ordinary indoor clothes, plus a thin fleece jacket with hood and a cotton hat, Teddy was toasty warm for a half hour outside in the stroller. His cheeks got a little chilled, but the back of his neck was even warm, and his hands -- inside the bag while he slept -- were nice and warm, too. Amazing. I didn't even put the rain/wind cover on. There are a ton of variations on this theme, usually set up so you can completely unzip and remove the top and leave the bottom in the stroller as extra padding. This one does not do that, but it does unzip to lie fully flat (dunno what good that would do anyone).
Checking out some similar items at JoggingStroller.com, I am only slightly shocked to discover devices to measure the mileage you put on your stroller, pushbar hands-free attachments, stroller locks (that is actually tempting, or would be if it weren't a fairly ordinary cable bike lock -- but this gets me thinking about how I might be able to use a decent bike lock on the folded up stroller to secure it. Hmmmm), a tire pump which is supposedly easy to use even on the valves on the small wheel of the stroller (if true, highly desirable; it is, unfortunately, backordered), and a wheeled piece of luggage that our jogging stroller would fit into that is supposedly checkable. Hmmm.
So Not Going There.