Have you ever used a e-ink device? I ask, because it seems you have some misconceptions about the technical details of e-ink devices. All the points i cited in your list would be horrible experiences with an e-ink device.

I will try to explain why:
Navigation:
You want to have a display of your car, where it is in a map and which way to go. Otherwise you could just use printed instructions. Current e-ink displays flicker each time they are updated. Color has not yet made it into commercial e-ink devices. So you have a constantly flickering display, for which you have to create a custom navigation app which offers at least some contrast between the map and the car and finally you will use quite a lot of power. Why? e-ink consumes power when its updated. Constant updates and its not much better than any other modern display.

At night you would have to illuminate the device to see your navigation, or you make it thicker and add an illumination layer.

Web Browsing:
Smooth scrolling is widely expected, not possible with e-ink.
Colors are missing, you can install redlight or flux and set it to full dark, giving you a black/red image, even with grayscale (redscale).
Browse the web a bit. You will see, many things a re now very difficult to read because of missing contrast.
Examples: lights in "help us keep on the lights" top right of maemo talk has nearly the same color as the background. The youtube subscribe button is invisible, with just black and white it will be way worse.

Taking still photos:
Similar to web browsing you will not know:
Did the contrast wok out?
Have I over/underexposed something?
Did the white balance work?
And zooming would suffer from issues like in navigation.

Email, typing, sourcecode, terminal:
Constant flicker will make you crazy, type fast and you will see spelling errors half a sentence later. Fast scrolling terminal output? You will miss half of it due to the refresh rate.

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E-ink is great and has its uses for reading or standby screens,
but it cannot replace an LCD or OLED screen. Not even for your restricted set of usage.

As the technology is quite new (as a focus of industry) constant progress is made.
There are prototypes which are impressive: Color, no visible flickering and 33 frames per second.
They also have disadvantages: Colors seem washed out, its no longer bistable (requires the image to be refreshed from time to time)

So it seems an e-ink device which suits your needs is 5 years of research away and its 10 years before a commercial solution may appear.