WASHINGTON: A UK-based company is developing the world's smallest emergency phone charging device which is just 1.3-inches in size and can be carried even on a key ring.

Devotec Industries is launching the product that is 0.9-inches wide and 0.5-inches thick on Kickstarter website, Gizmag reported.

The Micro Fuel charger features a standard micro-USB port, so it will be able to charge most phones.

The body of the product is die-cast aluminium. This means it is incredibly strong but still light weight, the company's website said.

The product contains an energy dense lithium-ion rechargeable battery which provides around 20-30 minutes extra talk time, or a few hours on standby, although that is dependent on the type of phone being used.

The device can retain its charge for anywhere between a month and three months before needing to be charged, and comes with a power switch designed to keep it from discharging needlessly.