Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
LearningSoft has used customized Linux-based handheld devices in an "assessment system" aimed at helping classroom school teachers create, administer, and score tests. Aimed primarily at grades three through eight, the "Indigo Learning System" uses Aeronix's $99 Zipit chat device running a custom software stack.
Ironically, the Indigo system was built on top of community-supplied Linux patches originally developed without much if any cooperation from Aeronix. Now, though, the hardware vendor is clearly realizing the benefits of community contributions, wanted or otherwise.