This is an enhancement requested at FOSDEM 2003. Here's an excerpt from a mail
message about this:

 * A shell! This has come up before and we kept telling people it's
inappropriate without processes, safe thread control (can you _really_ just
suspend/restart threads?), and frequently no filesystem. But people said we
should consider it as infrastructure so that _they_ can add shell stuff that
they want to.

Someone mentioned dash as a starting point... see
<http://v2dash.hypermart.net/>... but looking at it that can't have been right.
More relevant may be that it gives an idea of the commands a custom shell we
supplied _could_ provide.

A second but much more interesting idea IMO is to port TCLSH! That would be very
powerful, it's very portable, was even originally designed for an embedded
system. I like this idea a lot. It probably came from Bart of course ;-)
although I can't remember for sure.