Emergency alarm systems are standard-rated with exception to those that are designed to be operated by a disabled person which are Zero-rated enabling disabled persons to call for help in case of illness or injury.
VAT raises significant revenue to be used for public spending, on services such as the health, defence, and education. The extension of the z/r would have to be considered in the context of £50bn of VAT relief requests that Government has received since the EU referendum.
Extending the current VAT relief to all would come at a significant cost to the Exchequer, and there are no current plans to extend the scope of the relief already in place. However, the Government keeps all taxes under review.