Your online activity can now be tracked with your smartphones battery life.
You hit the power saver mode whenever your smartphone or your laptop goes low on battery.
All the features or apps that take up extra battery get disabled.

Technology like VPNs are basically more than enough to stop people from following a user around the internet.
However, those measures could be played around due the security problems in the battery software.
The website can then re-instantiate users cookies and other client side identifiers, a method known as respawning.

source: www.techworm.net