Plug-in Electricity Meter, Clas Ohlson in-store Liverpool usually £9.99, reduced to clear £1.99 instore @ Clas Ohlson

A plug in energy meter, so you can monitor energy usage and track down idling devices using too much energy. These usually go for around £10, with other models being anywhere from 10 to 20 quid.

It can show you usage, calculate cost based on programmable unit cost, watts, voltage and amps. It's good to at least have one to know what your devices are doing, especially when they are 'off' but may still be drawing a current, to help you identify items which need proper turning off, to avoid high energy bills.

Found in Clas Ohlson, Liverpool. Plenty on the rack as per picture.