I own a YotaPhone 2 since a little more than a year now, and I am very satisfied with it.
It's a dual screen from 2015 made in Russia: it has an e-ink screen on the back that can display both dedicated widgets and the android OS, like the normal screen.
The OS (Android 4 up to 6) has been adapted for the screen and special care has been taken to make the system consume as few energy as possible if configured so. Think of it as the phone you dumb down when you go on a week-long trek in the Siberian Taiga.
I love it because of the extreme readability of the screen under full sunlight. I don't need to find a shadow or make some with my hands in order to select a song in a playlist, check my position on a map or reply to a text while walking.
There are also some cool features, like mirroring the camera's view on the back screen so that people who are photographed can have a preview of the final result.
The phone can also flash your contact info on the e-ink screen before shutting down (since it's e-ink, the image gets persisted even though the battery is flat), just in case some good samaritan finds your phone.
And now that the YotaPhone 3 is out, you can find it for 150$.