Swi-x

On their site they claim this works with a range of alpine head units. Are these the only ones that it will work with?

website: http://www.pac-audio.com/products/swi.htm

If the HU uses an infrared remote control it will work.

anything with a remote? Cool thanks!

I didn't say that. Anything with an Infrared Remote.

there are different kinds? I've seen some with wired remotes, but what else would they use?

There are also radio frequency remotes. Rare but they do exist out there somewhere.