I guess its custom text, as in stick on buttons for just about any label you would need.

I use them in audio systems in unimportant rooms that need little control (dining room off kitchen, almost like subzones). If you have more than a couple sources, I would highly recommend the RK2. Although, it's not a fancy color screen, it does allow for separate pages to control different sources.

You can get creative with the RK1's, but will involve having to learn what buttons to press to do certain things. Lots of press and holds and flags to make it work well and someone who hasn't been taught how to use it would have no clue.