I am testing the Rachel 64GB USB image extracted to a micro SD card on a device called the ZoomGo. I just purchased a second unit used for $5. I see others listed for as little as $7 NEW including shipping on Ebay.
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Small and rugged
Only support 4 users!
Only supports Static HTML. - Still testing to see what else could work.
EDIT: The device can connect to a WiFi access point via WiFi and it seems to work well in that type of setup. I don’t know if that will expand the number of users that can access the device although I suspect it will. The experience thus far has been great. My biggest concern would be security on this device. I don’t have a good answer for that other then updating the firmware with something custom although it runs a variant of openwrt so likely possible if there was an interest.