Diverter, TempAssure???? What do I need for my shower?

I am remodeling our bathroom and want to install a showerhead and handheld shower fixture with a one handle control. How do I do this? Delta has the TempAssure line, but do I need a separate diverter on the wall, or can that act as a diverter too? Or, (as you can tell, I am clueless) can the diverter be just attached to the normal handle, or do I have to have a separate diverter on the wall?

I am just really confused by all the control options. I just want to be able to use the showerhead or handheld or maybe both.

Please help??? I don't know what to buy.