I've had iPhones delivered and not had to sign. I live in a small town where fedex or ups know us very well. If we aren't home they either come in and leave it in the house, or bring it to my husbands work. They're pretty awesome guys. Was waiting for a world of warcraft expansion one year and saw the ups guy at subway and he gave me my shipment right there.
I'm guessing the answer is "no". Just checked my tracking information online from work and it says "Delivered; Left at Front Door". Let's hope it's still there when I get home...
Supposedly it's signature required, but you could presign and leave a release form. Though again, supposedly, some drivers won't take those forms. So I guess it depends on your driver.