You could try the OpenPandora, or its successor, the Pyra.
I have an OpenPandora. Using it in freedom is a bit difficult, and it's a very weak device when you do (no graphical hardware acceleration, and no wireless of any kind). The way I set it up was to install a 3rd-party OS called "Pandian" (a slightly modified Debian) and purge a package which added the proprietary firmware needed by the wireless controller. To let it connect to the Internet, I use the small wireless adapter sold by Think Penguin. (Funny enough, the OpenPandora's built-in wireless, in addition to not respecting your freedom, doesn't work well at all, so the mini-adapter actually performs much better.)
But once you do manage to install and clean up Pandian, you will have a small computer with a mostly decent keyboard and a touchscreen that you can use either with a finger or with a stylus.
The Pyra is supposed to use Debian by default, so using that in freedom will probably be easier. Asking on the Pyra/OpenPandora forums,[1] I was told that the Pyra would have basically the same amount of respect for the users' freedom as the OpenPandora, with the caveat that full sound quality will require a proprietary firmware blob. So, no hardware acceleration, no wireless, and poor sound quality will be the practical setbacks of making it run entirely libre software.
[1] https://boards.openpandora.org/topic/18273-how-close-does-the-pyras-design-come-to-respecting-your-freedom/
