We used a similar harness for our two cats while they were getting used to our new neighborhood. They initially found the harnesses frustrating but became reconciled in a day or so. They did want to explore. However, once we released one up an apple tree with the harness on and she got hung up near the top of the tree. I had a fine time climbing up and retrieving her.
Now they roam about the yard on their own but if we were traveling we would certainly take the harnesses along.