80 Million Samsung S4s were produced in 2013-4. They are all past their warranty, and relegated to the trash. Just 1% would represent 800,000 phones. A perfect, resource, and challenge, for the Maker / Hacker.
Extend the lifespan of the S4
Discover the Dirty Tricks in the S4.
Samsung is renowned for its Bloatware. Make all Samsung Bloatware uninstallable. This will increase both Memory and Speed, as well as lengthening the product life, by eliminating the “out of Memory” timebomb.
Re-engineer / Re-purpose the S4
In order to increase the security of the young or old. A phone which can only dial, say, four programmed numbers, with photos to identify the people to call. E.g. for children it could be pictures of their parents that they can dial, for the elderly, it could be pictures of their children, their grandchildren, their doctor, or emergency services that they can dial.
Create a dedicated, full function, MP3 / MP4 player.