So there are a couple of options.
The first question is how do you want to control them? Via a DCC system or via "analogue input" (read switch or push button on a panel) or a combination of both?
Then there is the question of do you want to use a commercial option or a DIY option? The DIY option would require some sort of programming and electronic skill, which isn't for everyone.
I'm currently doing some work on a board that would allow for the analogue input method. There are still some bugs that need working out.
Niel