It's safe, secure and reliable. You will seriously need to expand on these points to get customers. Looking at the idea blind, I can't see how it can be any of these things. No pretty UI stuff will be needed until it's a viable business, and addressing these three concerns strikes me as paramount.
I can't imagine why I'd want to give a package to a person I've never met who has no obligation to deliver the package to it's destination. If I didn't care too much about the item being shipped... I wouldn't be shipping it.