It could be useful in India or African countries with not much access to energy. But I doubt people from developed nations would want this. It most likely offers nowhere near the experience of an LCD device. Remember, besides the lack of color issue, e-ink devices work best when the on-screen image is static, and not changing often.
My father does motorcycle touring and would love the same.
I have an old Sony Ericsson M600i symbian phone ( http://www.gsmarena.com/sony_ericsson_m600-1425.php ) I dig out for when I go travelling. The battery is still good for 10 days stand-by. It's such a pain to resync contacts, mail, etc... that all I really do is move the SIM over and use a travel email account.
If I could have the battery life of the old phone with the functionality of a new smart phone, then I'm very willing to sacrifice the screen quality to achieve it.