The developer and unlocked versions of the HTC One M8 are now receiving an update that enables the device's Extreme Power Saving Mode. This feature extends the phone's battery life by disabling all but the essential services, shooting users out of the standard interface into one that provides access to phone calls, text messages, email, calendar events, a calculator, and nothing else. This feature did not ship on the HTC One M8 out of the box here in the US, but updates are turning that situation around. The Extreme Power Saving Mode is joined by a few enhancements to the camera and gallery apps.
The build number is version 1.54.1540.9, and the download is roughly 118MB. Update away.