I have the PocketChip; great device. Recommended for sure. Together with come CHIPs you can do nice things. Sure for the same price as the PocketChip you can pick up a far more functional Android / Windows 10 tablet but this has a keyboard and you can replace anything in it yourself and do interesting hacking for both software and hardware.

Edit: (I bought the PocketChip for the introductory price; it's more expensive now but still cheap I find, especially as I would really like more people to make things like this... Is there anything else than the Pyra & this for handheld devices with a keyboard that you can actually order now and be quite sure you'll get it instead of throwing money away?)