[yumaikas]

They provide workable instructions for creating this effect on Andriod and iOS, as it doesn't require an app as such.

If an app does come out of this, it'll probably be more about setting greyscale for different other apps.

[atareh]

you're right!

i give instructions for going gray on phones on the website, the app we're developing is desgined to make grayscale easier (whitelisting certain apps that is useful in colour, like google maps, etc).