I don't think you can do this in the states but here in Japan, now, when you get something delivered to you (think UPS/FedEx) you can have them e−mail your cell phone. Unlike the states, cell phone e−mail is very popular here. Of course it helps that the phones have larger displays and better input systems.
Anyway, why would you want them to do that? Because, they will tell you, within a 2 hours time frame, what time they are going to deliver the package and if you are not going to be there you can go to their webpage from your cell phone and tell them when you will be their and they will re−schedule the delivery. Pretty cool!
I wish UPS and FedEx had this service. I know UPS never will as their motto is clearly "service, like we give a flying f*ck" but maybe FedEx will consider something like this. It seems like both companies would save money to not have to redeliver things.