Ask HN: Would a small touch interface on the back of mobile devices be useful?

It's an interesting idea, but I'm trying to imagine it while holding my phone, and it feels really awkward. The fingers behind the phone are supporting it, so I can't really "scroll" while keeping the screen stable enough to read.

Interesting concept though.

you could also put it on one of the device's edges

Motorola Spice has a little switch at the back.

It let's you scroll and click.

That would be an interesting idea. Isn't there already a controller for some console that implements that?

Edit:

It may be the Wii U, I'm not sure.

I think SONY PS Vita has one on it's back.