What to get for 3 way dimming?

You need a neutral for that switch. Unless you have k&t wiring (very unusual in the US unless your wiring is over 80 years old) there’s a neutral in the wall somewhere, but you may need an electrician to fish it out for you.

Cooper makes one that doesn’t require a neutral, but it will only work with incandescents. (There’s an older GE that doesn’t need a neutral, but it’s been discontinued.)

http://www.homeseer.com/compare-z-wave-dimming-wall-switches.html

These days if you want a networked switch, you’re much better off with a neutral.