Two choices I see:

1. An AOSP derivative, reverse Linuxed as much as possible. Package manager, proper terminal. Maybe even a backwards hybris, allowing emulation of a full linux environment. Supported on top of cyanogen, or even installed over a rooted Android. This thing truly unlocks devices, letting them become the sort of things that we read about in news articles about N900 hackery or more recently the Raspberry Pi.

2. A feature phone powered by tears.