Can anyone provide ideas of what this can be used for?
(Just to clarify: I am not trying to dismiss this as "useless". I am genuinely interested about knowing about use cases: in part because embedded systems or low resource self-contained systems are not my area of expertise).
This is a genuine question but in the following sense.
I see it asked today more like "What of the programs that we've already think of by today can we run on this? With an implicit answer that it seems so underpowered for anything non trivial and we already have more powerful systems so why bother with its limitations?"
When I was starting to learn about computers everything about them was cool and awesome (later but soon enough I've learned later that they do games as well).
But if I would have been asked by my father what good were they then I would have not have an answer that would be acceptable in the 'business' sense. Computers were cool in themselves. The process of hacking them was its own reward but my father would see me typing or playing games.
The most important realization for me was that I could make them do "anything" that I could think of. The realization that I was not limited in the space of programming was empowering.
So yes. Running most of today's programs doesn't make sense on it. But if you can see it as a playing (safe exploration) ground then the question is irrelevant. The most important issue is that playing may be the only thing that would allow you to imagine applications that you would not be able to imagine otherwise.
I have no expertise in this area, but I've been fascinated by the uLisp project and hope to get into it as a hobby.
Its use cases are probably similar to Arduino and other single-board computers, to interface with many kinds of hardware I/O, sensors and signals. I imagine the Lisp Badge has unique advantages and constraints, due to its choice of components and form factor.
Since it has a display and keyboard, an idea that comes to mind is: programmable calculator for education.
And maybe for professional niches - that require, I don't know, certain kinds of common calculations, formulae, graphs, to be done "on-site" (somewhere awkward for carrying laptops, but a smart calculator in a pocket would be handy).
From its size, cost, and simplicity of hardware/software design, perhaps it's suitable for computer/engineering education - including for beginners, children, or in developing countries.
(Just to clarify: I am not trying to dismiss this as "useless". I am genuinely interested about knowing about use cases: in part because embedded systems or low resource self-contained systems are not my area of expertise).