There are various brands of stroller boards....I don't own one but they look neat. This is one:
Amazon.com: E-Z Step Universal Stroller Wheel Board: Toys & Games
As for the convenience of a travel system, infant car seats hook on to other brands of strollers, not just the one that comes in a travel system. For example, this is my brand of stroller with an infant seat on it:
BOB stroller, Graco car seat. No big deal.
The thing I LOVED best when DD was little and we were just going to the mall was the snap n' go stroller. It's not a REAL stroller but rather a frame for your car seat. Because I had a c-section I didn't want to be constantly lifting a heavy stroller. Also, when they're in the car seat you don't even use the other seat part of the stroller. We had ours given to us but they come up used a lot. They look like this before you put a car seat on:
And with a car seat:
Here they are at walmart:
Baby Trend Snap N Go Single Stroller - Walmart.com
This is the stroller / car seat combo we're registering for.. the car seat snaps into a base that's already seat-belted into the car so no worries about it not staying buckled it or coming loose with each buckle, unbuckle, buckle, unbuckle.
And it just snaps into the stroller.
I can't believe all the new strollers they have come out with! I really like that they sell lightweight travel systems now because the old ones used to be so heavy. I still have no idea what I'm going to get. Really liking the new baby jogger city select that you can add an extra seat to.