Our companies Proof Of Delivery system uses that sort of arrangement. more or less.
< uses a Treo running a barcode scanner, signature on screen, Camera for still photos of delivery left @ door, with near instantaneous email of Proof of Delivery through Sprint.
Cell phone works, as I get incoming junk calls from time to time. Company only allows 911 calls with no charge.
Also uses a separate handheld PTT Motorola for voice communications w/ disp[atch.