We just came across this neat contraption. It is called the Fropper by International Playthings. It is for children 18 months+. The two level seat has a spring system that allows your little one to bounce as he strolls down the sidewalk. It also folds to a fraction of its size, which makes it great for storing.
Where was this when we were kids? This looks like a lot of fun. It retails for $69 and you can find it here.
With summer on the horizon this would be a blast for your little one. Not only does it sound cool, it looks cool too! So, get to Froppin'!!