The right time to leave a child at home alone is when the child decides. All my kids felt comfortable with that thought around the age of 12 I never left them. However, for more than one in a half an hour tops ( my problem; my rich imagination) nor would I have ever left a toddler in the care of a child. There were also ruling like not opening doors to strangers, etc. Bottom line: It depends on the willingness and character of the child. Aside from it, I have provided them a mobile application for safety and protection. Just pressing a button they can notify and alert friends, family and myself if ever in danger. If needed, the call will be routed to the nearest 911 dispatch. Extra protection for your kids check this out
http://Safekidzone.com/ 
