So you would like to livestream with 2 smartphones? The Livestream Dual Smartphone Steaming Grip has you covered. It supports smartphone up to 85mm wide. Thanks to this smartphone holder, you will be able to stream to Periscope and another platform at the same time. It holds your smartphone in portrait and landscape positions.
You can move the adapter up and down to adjust the angle. It is also possible to attach a LED video light to enhance your stream. Costs under $30 at this time.