Embedded system scripting
I've looked into eLua and also an embedded python interpreter for some projects I'm working on in my day job. We're developing a base control system, but these systems go out and are customized extensively in the field. Rather than require the end use to add extra processing modules, we allow them to configure our system, and in some cases, write their own features. Since it is prohibitive to have end users reflash in the field (they could easily brick things), we provide a scripting interface.

Currently, we have a proprietary language that is compiled into bytecode and churned through in order by the kernel, but we are trying to make things more standards compliant and easier to maintain.

Here's a comparison of different interpreted languages that can run on 'bare metal': https://stackoverflow.com/questions/1082751/what-are-the-available-interactive-languages-that-run-in-tiny-memory

Generally, once the device has been flashed once in the factory, we don't want to have to reflash. It is slow, prone to errors, and difficult for end users. In order to extend functionality after production, some sort of scripting extension is a good solution.