We used harnesses something like that for our ferrets. Some of them loved going out on walks and that was about the only way it would work. It didn't take long for them to get used to having the harness put on. Sometimes they'd wriggle out if they got real excited about something. Mostly it worked pretty well. Those look like velcro. Ours were more like buckles.
I have one for my bunny but it is just kind of cleverly bucked string. He hates getting into it (esp when I put the loop over his head) but doesn't seem to mind once he has it on. Then I can take him to the park and people can laugh at us.
I can say with certainty that even though they often market these for guinea pigs as well as bunnies, the pigs will not stand for it. They are not interested in obeying...they like to run around freeeeeeee!