At $1495, the Taga Bike may seem like an expensive proposition, but given the prices of bikes and baby trolleys, I would get one. Also, this thing is bloody awesome: it transforms from bike to trolley in 20 seconds!
It's made with aluminum, with a Shimano Nexus Inter-3 internal gear hub, disk brakes on both front wheels and a roller brake on the rear wheel. The Taga Bike has 16-inch wheels and can be set into two positions in stroller mode and two positions in tricycle mode. You can load this thing with accessories, and even customize it for twins!