A new wristband that tells users when they have had a healthy dose of sunlight has been developed in the US.
While exposure to sunlight provides vitamin D, a lack of protection from harmful ultraviolet (UV) rays can lead to skin cancer.
The UVA+B Sunfriend wristband is designed to let users walk the fine line between too little and too much sun without the use of sunscreen.
It is the world's first true gadget for daily UV activity monitoring, its makers say.
"We designed the SunFriend to help people optimise their vitamin D and reduce the incidence of skin cancer simultaneously," they said.
The waterproof wristband contains patented, NASA-inspired UV sensors with LED indicators that light up as UV exposure accumulates, before flashing once the safe limit has been reached, 'Gizmag' reported.
The user sets the device to their skin tone and sensitivity and it then constantly measures both direct and reflected UV exposure.
The concept gained traction after inventors Shahid Aslam and Karin Edgett won best Consumer Product and Most Popular Vote awards at the 2011 Create the Future contest, run by NASA TechBriefs.
Aslam and Edgett then put together a team of engineers, scientists and marketers and set about testing prototypes with the aim of developing UVA+B Sunfriend as a commercial product.