Leash Safety Harness

When I have my own child,I want to ''leash'' it for safety when I'm around busy places,like the mall or where there is a lot of people.
I would just do what parents usually do,''hold the childs hand'' but sometimes you need both hand and if you let go to get something and turn around and your child took off somewhere.
You could tell them to stick with you,but you know how little kids are.

Alot of people find it cruel,I find it safe.
What do you think?

If you don't know what I'm talking about heres a picture

http://www.designerkidsandbaby.co.uk/images/uploads/babyaccessor/t351_9ba1b0ab7908800e48945d8257522eaf.jpg