This hand rig works for iPhone 7 Plus and below. It does require a flexible mobile phone tripod mount but we had several of them laying around in the office. You can get one for $6 here:

https://www.amazon.com/dp/B00XTHBE6A

This rig uses the base of the Structure Sensor Tripod mount.

Structure Sensor Tripod Mount http://www.thingiverse.com/thing:856239

When we saw this Sensor Grip, we knew that we wanted to remix the handle.

iPhone 5,6 Structure Sensor Grip http://www.thingiverse.com/thing:958897

We didn't have the hardware for the tripod and connection mounts so a little post print sanding and Loctite glue takes care of the remaining steps you need to make your own. This is just our first version and future updates are coming.

Print these items:

HANDLE TRIPOD NUT (3) BOLT ROUND BOLT THREAD

You could go to Home Depot to source the NUT, BOLT, ROUND BOLT but if you want to save a trip. Print all. Slight sanding and Loctite glue will get you there.