Check out the blog attached to the link below. It has info on lockboxes as well as other information on doing a FSBO. Good luck.
If you are referring to the electronic boxes that are used on houses for sale by Realtors they are only functional for Realtors. You could buy one but would not be able to open it etc.
Do you have a property in the Phoenix market you want to sell? Could you tell me more about what you have to sell?