Don't force the technology worker to use one brand for a SmartPhone (Blackberry, Android, MS Windows, Apple). Leverage what the user is already buying. Give the end user a set amount of funds to purchase technology every three years.
Following suit with how the other official Lines of Businesses operate, make Mobility Shared Service Centers that truly become experts in acquiring, managing, deploying, repairing, etc mobile technology. These shared service centers could aggregate volume of purchasing to get better pricing, and could "field" this technology in support of their peer agencies.