Having first-hand experience, I know what a hassle it can be to travel by air or rail with an infant. You need a small army of Sherpas to carry the car seat, the diaper bag, the toys, the snacks, the luggage, the laptop, not to mention the baby, from point A to point B. This is compounded by the limited number of carry-on items you are allowed, plus the problem of getting all of the aforementioned items through the security check point. (And don’t get me started on the whole "is that breast milk or a flammable liquid" issue!)
Tote-a-Tot is touted to help consolidate all your travel accoutrement into one pull-behind package. It appears from their website to be a modified diaper bag type device, which hangs from the underside of your rolling suitcase. It has long straps that then encircle your bag in order to attach your infant car seat to the top. This seems to eliminate the need to carry a stroller, which you have to relinquish at the end of the jetway at any rate.
In theory, this device seems to help consolidate everything into one convenient roll-around package. In reality, do you really want to be dragging your baby behind you through a busy airport and/or train station? Will it work with a rolling laptop bag? And is there a "tail-gunner" add-on available? Tote-a-Tot lists for $29.95 and is available from their website.