Is there a camera app that will meter/adjust lighting to the object that you focus on?

[SKW91]

When I take a photo with my iPad's stock camera, it will automatically adjust the lighting to whatever I have focused on. Most cameras have "spot metering" which will adjust based on the very centre of the photo, but don't adjust to whatever you touch-to-focus on if it's off-center in the photo.

Does anyone know of an app that has is feature? Or at least what it's called - I'm having no luck googling it.

Thanks!