Although with some reservations

Neoprene provides good sealing (tempered back completely dry pouch)
The iPhone can be manipulated relatively easily under the shield.

There are just two small points which pay attention to:
- The slot in which you insert the iPhone remains open. I run including rain, so I'll add a waterproof flap with a few stitches and velcro. At 20 euros, it could be done by default
- I have thin arms, it is the lower limit (25cm approx.). Below the cuff really may fall.

Hint: it may seem silly, but to remove the iphone, first push from below, as drawn from the top is almost impossible.