Watches no longer just show the time. Smartwatches can be used to check heart rate, measure the number of steps taken and check e-mails. Researchers at ETH Zurich are now using these digital helpers for a new function: the green light emitted by the watches stimulates insulin production through the skin - at least in mice.

The team developed a molecular switch and coupled it to a genetic network in cells. Depending on how the network is equipped, it carries the blueprint for the desired proteins. When green light hits the cells, production begins.

The researchers tested their system both on a bacon rind and on living mice, in which they implanted the cells. Accordingly, they were able to turn on the activating green light by starting the smartwatch's "running app."

However, it is likely to be several years before the technology reaches everyday clinical use. The cells used would have to be replaced with the patient's own cells, the researchers said. The system also has to get through the clinical phases before it is approved, they said. The hurdles are high.