Philips is developing the technology as a contactless system to keep a virtual eye on hospital patients, such as newborn babies, who might find conventional monitors distressing.

ECONOMIST: Facial monitoring

But the contactless payment system will not include daily price capping, which means if it is used several times in one day it will not stop charging once a passenger reaches the cost of daily travelcard.

BBC: London buses offer contactless card payment

Being wrist-mounted, a watch is always close at hand, which makes it particularly convenient when operating contactless readers on public-transport systems (such as those used by London's Oyster system).

ECONOMIST: MONITOR