There are other sites for childish games.

I expect you mean a bi- or probably tri-cycle that is combined with a baby-stroller, that is, the child carrier is designed to the front of a pedaling-seat and rear drive-wheel. In third-world countries, bicycles that push a load out front are common, so I think your idea would be easy to build. Unfortunately, I don't see it as particularly safe for a little one, that is, if I've interpreted your 'stroll-cycle' correctly. But in the US it's common to pull kiddies in a little sort-of wagon hooked to the back-wheel, so that the bike would crash before the 'stroller'. Not really any safer, and you can't see the kids.

this sounds like something from ( i think it was) popular mechanics, like a treadmill on wheels, which just gives you a mechanical advantage. it was the dumbest idea i had ever seen.

http://withleather.uproxx.com/2008/11/thanks-science