Here's how I would do it: I'd sell/give away clip-on baskets with a fat QR-code or similar imprinted on the inside bottom (or with embedded iBeacon-like-tech o

Here's how I would do it: I'd sell/give away clip-on baskets with a fat QR-code or similar imprinted on the inside bottom (or with embedded iBeacon-like-tech or even infrared lights similar to the Wii) to all customers who want to use this service and ask them to attach it to a window-sill, preferably upstairs or to the the back of the house. This would allow the copter to make a secure drop. As the copters are weight-limited anyway the baskets could also be. It's also worth noting that as this service is for urgent items (why else would you pay extra for a 30 min service) why would you need to worry about the recipient being out? With GPS built-into mobile phones, 4G internet, bluetooth and iBeacon-like tech you could inform the recipient just before delivery or even better and it directly to them (or a special basket placed on the ground).