New Delhi, June 30 -- That old iPhone sitting in your junk drawer could actually be working right now. Turns out, it could even help scientists track dolphins or make your city's buses run on time.

You probably upgrade your phone every couple of years. Most of us do the same thing, which means there are billions of phones just sitting around. Meanwhile, we're building data centers that consume massive amounts of energy to handle our digital needs.

Some researchers in Estonia looked at this situation and had a realisation: what if we could turn those old phones into tiny workhorses that actually help run our digital world?

The process is simple. They take an old smartphone, remove the battery for safety, plug it into external power, pop...