One case in point is the Horizon MiniPak, which was launched in 2010 with a power capacity of 12 Wh. The Upp ups the capacity with 25 Wh and works in conjunction with an accompanying app that provides device info and details of locations at which spent cartridges can be exchanged for new ones.

Intelligent Energy, the UK-based company that developed the Upp, claims that each cartridge provides an estimated five smartphone charges via its USB port and can easily be swapped out for another when depleted. Once the mobile device has been recharged, the Upp will automatically switch off so as to avoid wasting power, or can be set to charge a device to a specific level.

This is done using the app, which is available for iOS and Android devices and allows users to put the Upp into flight mode to prevent continuous charging, as well as showing exactly how much energy the current cartridge has left and what the remaining power can be used for. The app will also use GPS to locate the nearest outlet to purchase new cartridges, and also provides support materials and access to customer support.