Depending on how you want to do it, you can just add a micro controller to one switch. That might be more cost effective. However I personally prefer to replace the switches with Z-wave myself. If you do replace, you WILL have to replace both as 3-way Z-wave is a different animal than 3-way normal. Rather than retype a bunch of stuff, I’ll refer you to this thread:
Lots of good info there, including from pretty snazzy drawings from yours truly.