Would this device seem worthwhile to you?

It would depend on the cost to purchase the device, I think. If it were not overly expensive, it would be nice to have for trips to the local grocery and back. If it were expensive, then I do not believe it would be something I would be interested in. It would be a nice way for us all to cut back on some gas for those local shopping runs if it could be manufactured and offered at a reasonable cost. That would be the only cirstance I could see a use for it though, unless you are fortunate enough to live within 10 miles of your workplace.