If you setup a calibre content server, you can access your books on the go -- another alternative is in my sig.
Calibre Companion is a way of organizing books on Androids, and opening them in the right reader apps. It will not help you get books onto an E-ink device.
ETA: except for some of the small-name Android E-ink tablets that have recently started popping up, and even then, they aren't your Kindle.
Still maybe worth a look, a bunch of people have expressed enthusiasm about them... but eh, why do you need to spend money on
another device? The ones you have work fine.
(All evidence to the contrary, of course,
some people are collectors.)