My buddy owns a small courier company (which I helped found a few years back). I'm about to write a piece of android software for his couriers to solve exactly

My buddy owns a small courier company (which I helped found a few years back). I'm about to write a piece of android software for his couriers to solve exactly this problem: when they get a "nobody at home" situation, they'll have to post a note on the door, then take a picture of the note and scan the package, while the software records the GPS (or network) coordinates. A HTC Wildfire is around $50 with subscription, and once all couriers have them we intend to extend the system as much as we can. Lots of cute stuff should be possible with a combination of camera/barcode reader/gps/internet device.