Well, not quite, but he does have a new vantage point on walking trips now.  Calvin has pretty much outgrown the sling and the front carrier, and he sits in the stroller just fine, but it's hard to see the zoo animals from that position, not to mention that strollers don't do park paths very well, so we got him a backpack instead.  He loves it.  We tried this new method of travel while out for our evening walk Monday night and you'd think we'd given him a space shuttle!  He reached for every tree as it passed him by, continually poked and grabbed at his dad's hair and neck, and laughed and chatted the whole walk (a great step up from his usual zombie-like behavior when riding in the stroller).  It was clear that he could see the ducks better when we got to the pond, too.  Of course it's now cold again, but we're sure outdoor weather is just around the corner and this will definitely be our first choice for outdoor travel from now on!