HTC One M8

Following similar updates by some of the U.S. carriers, the first software upgrade for the HTC One M8 has started to arrive in Canada. We're seeing an update to version 1.55.631.4 on our Rogers M8, which adds the new power-saving feature alongside "camera and gallery feature enhancements."

Extreme Power Saving mode was available on European HTC One M8 devices at launch, but handsets in the U.S. had to wait for an over-the-air update. From our HTC One M8 review, here's a quick rundown of what the super-low-power mode actually does:

Basically it shuts down all connections but still allows phone calls and texts to come through. You can manually refresh e-mail if you want — but only in HTC's e-mail app. Your smartphone essentially is turned into a dumb phone. And to make sure you don't cheat and try to actually make it do things, the M8 gets a new home EXTREME home screen, with shortcuts to the Phone, Messages, Mail, Calendar and Calculator apps. To exit EXTREME mode, you'll need to hit the dedicated "Exit" button.

HTC says that with only 5 percent battery remaining, you can eke out 15 hours in this EXTREME mode. On a full battery? It'll last something like a dozen days. We'd consider this to be more of an emergency mode than EXTREME, however.

More: HTC One M8 review