The Liquid Level Indicator can be placed on a mug to help prevent hot or cold liquids from overflowing while making a drink. The indicator detects two different levels of liquid. It emits an intermittent beep and series of vibrations to indicate when the cup is nearly full and a faster beep and continuous vibration when the liquid has reached the limit of the mug.
It should be tested regularly with cold water before using to make sure the battery is still fully operational.
This device can be purchased online through the National Council for the Blind in Ireland or the Royal National Institute Of Blind People in the UK.