ServiceCall is a system designed to make it easier for people with mobility difficulties to use shops and services. You aim a small infrared transmitter to activate a receiver in the window of a petrol station, bank, shop etc. It is most common in self-service petrol stations. All motorway service areas have ServiceCall.
Click on the external link on the right of this page to the ServiceCall website for details of how to purchase a transmitter and the location of ServiceCall points around the UK.