> The hardware is lustworthy, though the resolution could be higher, it's just a shame there's no SDK. The buttons on the front look very old school Androidish.

I have a 10" e-ink device with 1200x825px which is perfectly fine for A4/letter-designed PDFs, so I'd say the resolution should be fine. I also have a 10" notebook, and the readability is considerably worse at about the same resolution, so I guess e-ink resolutions are not really comparable with lcd resolutions (the pixel layout is quite different: http://farm4.static.flickr.com/3090/2286311679_f98bdba47f_m....).

Which device do you have? The Kindle DX is 9.7"

Visionect sells developer-friendly (SDK included) 6" and 9.7" devices starting around $500: http://www.visionect.com/

Don't know about the GP, but I have an iRex DR1000 (http://en.wikipedia.org/wiki/Digital_Reader_1000) which was perfectly sized for reading A4/letter papers. But it is bulky and has no wireless connectivity.

I have an Onyx BOOX M92: https://onyx-boox.com/productsinfo/onyx-boox-m92-black-pearl... It did cost 300€/420$ a year and a half ago. The alternative at that time was the Pocketbook Pro 912 (http://www.pocketbook-int.com/de/products/pocketbook-912) at around the same pricepoint, but that seemed less open (technically both run Linux, but Pocketbook didn't publish their modified sources).

    it's just a shame there's no SDK

I noticed that the battery life is 3 weeks. Given the size of the product (not large), it's safe to say that they get that battery life by doing as little as possible. It may be that they don't have enough processing power to run any sort of apps, or if they did, it would drain the battery so much that it would ruin the device.

With that said, it would still be cool to try. It should at least be able to support a calculator.

Nah. Nook Simple Touches can be rooted and run Android just fine. As long as wifi is off (thus disabling the vast majority of app background syncing / periodic updates) it easily lasts a couple weeks. For that you can run a surprising number of apps just fine in a ridiculously-limited available RAM space. I can't imagine this would be anywhere near as slow as a NST, so it should be able to do just about everything except play 3D games and visit crazy-bad websites.

As long as you don't busy wait and only update the parts of the screen that change it's not too hard to write software which doesn't impact battery life too much.

EDIT: To add, obviously minimise network connections. And if you do need them, batch them.

The test model I used for a month only needed one charge, it works a lot like the black and white kindle and the document stays static on the screen and the device only really turns on when you write on it or turn pages.

> The hardware is lustworthy

what part? I have a 1440x1080 ereader retailing at $170.

Which one?