USPS Strategy

So, I've been analyzing the framework of the United States Postal Service. Laura went to mail a book she sold on Amazon.com, and I thought "How old school. Isn't there a better way to do that?"

So I came up with my own business idea. It's Redbox, but for shipping stuff that you sold on Amazon.com or eBay. I call it the Box Stop. I'll put Box Stop Machines outside the post office, business districts, etc... People then go there after they get their sale confirmation from the online auction or retailer. You can pick the packaging material you want, print shipping labels, pay postage, and weigh your item, all at this convenient location. Then you can leave the box there (in a secured location) and USPS will come pick it up.

Well, I wanted to see if anything would be a "barrier to entry" for this idea. Sure enough, USPS, UPS, DHL, and FedEx all have online shipping solutions. But I think there may still be some viability for this semi-online yet semi-brick and mortar idea. Thoughts???