A cancer research team hopes to build a network of more than 100,000 UK smartphones to help process data while their owners sleep.
Phone owners can get involved by downloading an app and donating some of their wi-fi or data plan.
The handsets will need to be switched on and charged for six hours per night.
The aim is that they will form a huge network that processes data about different drug combination, using an algorithm built by the team.
It would take over 100 years for a single desktop computer to process the amount of data involved, the researchers said.
"Cancer research progress is slowed by a lack of access to supercomputing," said Dr Kirill Veselkov, from the faculty of medicine at Imperial College.
"It's needed to complete analysis - but it's limited and costly.
"This is a great example of a citizen science project - with members of the public directly involved."
The project, called Drugs (Drug Repositioning Using Grids of Smartphones), is a collaboration with the Vodafone Foundation and is expected to run for two years.
Dr Veselkov's team is searching for new combinations of existing drugs that can be tailored to cancer patients' individual genetic make-up. Each one is unique.
"Let's say there are 10,000 drugs, with different combinations - that's a trillion possibilities," said Dr Veselkov.
"If you want to crunch these possibilities, it could take over 300 years. Harnessing the power of 100,000 phones, you can do the same in two or three months."
The Dreamlab app it will run from was originally developed in partnership with the Garvan Institute in Australia for a similar purpose in 2015.
Another scheme, The World Community Grid, run by IBM, uses the computing power of volunteered devices to research many different illnesses.
Data can be sent to the phone via either wi-fi or mobile data, with a cap of 500MB per month.
No data is taken from the device or any apps installed on it.
"People forget that the processing capability of a modern high-end smartphone is as powerful as a computer from only a few years ago," said analyst Ben Wood from CCS Insight.
"It makes great sense to try and harness this resource, particularly when a phone is sitting doing nothing overnight other than being charged for the next day's use."