My latest add-on Gear Tracker is coming along well. I'm having some issues with getting the UI to do things the way I want it to. I mostly just need it for the initial setup so you can have your saved armor sets named whatever you want. The way I was originally thinking about doing it was extremely complicated. I was going to compare the gear you have equipped to whichever gear set you specified. Then I looked more into it and realized if I get the player to tell me which set they want for which spec they're playing, then I can just check to see if that particular equipment set is equipped.
I might also add some other things, like checking raids vs pvp. I'm not sure what other features I want to add right now but I'm definitely up for people giving me any sort of ideas. Currently you can find the project on GitHub. Once I finish fixing the UI I'm planning on putting it up on Curse so people can easily keep it up to date.