I use Tophat on a Nook e-reader with B&W e-ink display. I gladly forego color for the size and sunshine-readability of this display. The Nook runs Android 2.x and they don't make them any more, but hopefully it'll keep running for some years. A disadvantage of the Nook is that it lacks an internal GPS, I've used an external USB GPS puck connected via an OTG Y-cable, now use a serial GPS module that I hardwired into the Nook's motherboard. The latter is more reliable, but the soldering job is demanding.