iPad apps don’t have access to a single physical button, so an app developer found a way to hack one on. Astro HQ, the company behind the drawing app Astropad, uses its latest app to turn the iPad’s camera into a button: you tap the camera, and an on-screen panel slides out; tap again, and it’s gone. It’s a really clever idea that allows controls to be taken off the screen, freeing up space.

Of course, this approach comes with a major downside: the camera has to be on and analyzing the entire time. That poses some potential battery issues, not to mention privacy concerns. Astro says it’s addressed both. It claims to blur camera imagery “to the point of not being able to see any data coming in,” so that it’s only looking at whether the camera turns dark. As for battery life, Astro says the camera button uses less than 1 percent of the iPad’s CPU at any given time, so it theoretically won’t make a huge dent beyond the app itself. The feature will also be optional.

“No one has used the camera like we are doing.”

The camera button will be part of Luna, a new app Astro is making that turns the iPad into a wireless Mac display (with the help of a tiny dongle). Because Astro doesn’t want to take up any of the screen with controls and toolbars, it decided to make a pop-out menu that hides controls away when you aren’t using them. In its previous app, Astropad, Astro used a floating button that you can move around the screen to someplace out of the way. But it was never truly out of the way or truly convenient, leading Astro to search for a better option.

That better option ended up being the camera button. Astro is still trying to figure out what it’ll offer as a backup for those who opt out of using the camera option — it had planned to use the iPad’s volume buttons, but realized Apple doesn’t allow that — so it’s possible something like the floating button will still stick around. There’s also the question of whether Apple will allow this novel use of the camera. Matt Ronge, CEO of Astro, says he thinks it should be in the clear.

“We looked through the App Review guidelines, and we don’t see a reason why the Camera Button wouldn’t be allowed,” Ronge writes in an email to The Verge. Ultimately it’s still Apple’s choice, he says, but “other apps have done similar things with the proximity sensor on the iPhone in the past (iPad doesn’t have one), so there is precedent there. However no one has used the camera like we are doing.”

Luna is supposed to come out in May. Astro is currently raising funds for the app on Kickstarter as part of a campaign that closes tomorrow. It’s already at 20 times its funding goal.