Best thing is probably an iPod Touch or iPad Mini without cellular (I'm pro iOS vs. Android, mainly due to secure element and iOS > Android security; there's an

Best thing is probably an iPod Touch or iPad Mini without cellular (I'm pro iOS vs. Android, mainly due to secure element and iOS > Android security; there's an argument you could use a secure element plus a new ROM on Android devices to surpass iOS), with a wifi or bt or usb link to an external wifi-4g modem or wifi-wifi router (mifi, portal, whatever).