Of all the interesting technology that exists within the world of the Guardians of the Galaxy, the most interesting may by the yaka arrow, the weapon of choice used by Yondu. It's a flying arrow controlled seemingly via Yondu's voice, specifically, his whistle. Now, James Gunn has revealed some details about exactly how the system works. According to the director...
Side note on the yaka arrow: the whistle sound is picked up by the headpiece and is transmitted wirelessly to the arrow.
We gained a great deal of additional information about Yondu's arrow in Guardians of the Galaxy Vol. 2. In the film, Yondu's headpiece is damaged, and without it, he no longer has control of the arrow. James Gunn explains on Twitter that the headpiece is the part that actually picks up the sound of Yondu's whistle, which it then translates into control of the yaka arrow wirelessly. The wireless range of the headpiece is quite significant, as we see the arrow traveling all over the place in both movies, taking out everybody in the blink of an eye.
Considering how powerful a weapon it is, one might wonder why it isn't more widely used among people throughout the galaxy. James Gunn also explains why this is. Apparently, while the technology that's built into the headpiece is fairly standard tech, the arrow itself is not.
2nd side note on the yaka arrow in explanation of an unnamed spoiler: the headpieces are fairly common/simple; the arrow is incredibly rare.
Specifically, James Gunn explains later on Twitter that manipulating the technology built into the headpiece is fairly easy and it's something that lots of people can potentially do to meet their own needs, however, the arrow itself is rarer. It's not the sort of weapon one can just keep a stockpile of in case one breaks. As Gunn says, this detail is important for part of the story, though we don't need to get into exactly why if you don't already know.
The fact that the arrow is rare also helps to explain why controlling it isn't the easiest thing in the world to do. In a post-credits scene in Guardians of the Galaxy Vol. 2, we see Sean Gunn's Kraglin attempt to control the yaka arrow himself. It doesn't go well. While the communication between Kraglin, the headpiece, and the arrow works, being able to get the arrow to do what you want takes practice. If the arrow is a rare weapon, then it's unlikely Kraglin has had much experience with it.
If the headpiece technology is commonplace, it will be interesting to see if we see more uses of it as the Marvel Cinematic Universe moves forward. We're sure Rocket could find some interesting ways to use it.
