Plug & Pop is the name given by LG for the app bar that appears onscreen when plugging in headphones or a USB cable on the stock ROM. It contains 4 customizable apps that you can launch. It's a nifty addition but I wonder if it can be implemented as a user app.
Um.. So like I said.. And yes, there are plenty of market apps, Tasker, etc.
https://play.google.com/store/search?q=headphone plug
Other obvious search terms..