[kbart]

"A good tinfoil hat approach is to use an iPod touch running an end-to-end encrypted messaging/calling app of your choice, connected to a secure hotspot."

Yes, but it's not much of a phone if it's WiFi only. You could use any laptop for such scenario as well.

[jwfxpr]

You could, though the attack surface on a laptop is arguably much larger than that on an iPod. And considering most security-conscious users are unlikely to use a classical cellular phone call for a sensitive conversation, it's actually pretty comparable to a phone, considering your hotspot can be as dumb as you like. An iPod + a prepaid portable hotspot is a damn sight more usable on the go than a laptop.