Smart Battery Case, a $99 (£79) add-on for the iPhone 6 and 6s that packs an extra 1,877mAh battery into a… curious-looking silicone frame.

Pros

• Extends the battery life on your iPhone 6/6s

• Acoustic port makes audio sound better

• Comfortable to hold onto

Cons

• Odd-looking design

• Expensive compared to the competition

• No on/off switch for the batterY