That is a
Phil & Ted buggy. It's about $800 dollars. Everyone (

--except me) has one in the city. There's another similarish design by Valco but it's also astronomically expensive.
Here are some thoughts on tandem strollers from a mom who has used them for about 6 years now. (Unless of course you can spend $800 on a stroller?!) Side to side tandems are much easier to push than front to back ones. However, for a toddler (which Scarlet will be when you have #2) and an infant I highly recommend a sit and stand. They're super sturdy (it has survived 5 years being dragged around on the NYC subway system and we still have it!). And they come with an infant seat for the front. The back is a bench (w/straps) so that the toddler can sit or stand. Not a jogging stroller I realize, but I used to jog with it easily.
HTH