Thanks to TheServerSide I have had significant interest in grash, for which I'm very grateful. It's great to see that after only two weeks from the initial idea, I have so many positive suggestions and enhancements to think about.
Marc Prud'hommeaux has directed me towards his wonderful wrapper for streams, called jline, that allows grash to provide line editing and command history.
I have released a new version (grash 0.0.0.5) which now includes this facility by default, both from the command line (java -jar grash.jar) and when embedded. If you have any security issues with this amendment when embedding grash, I have provided a new constructor that allows you to turn this facility off. Marc has very kindly relicensed jline as BSD, so grash is still fully available under an Apache2.0/BSD style license.
On Unix and MacOSX you can simply use the arrow keys to navigate round your most recent commands (on Windows you will have to use CTRL-N/CTRL-P due to an issue in jline). The commands you type are persisted (beyond the session) currently in your home directory in a file cunningly called "~/.grash_history".
I'm quite excited that jline also provides the potential for command line completion (a.k.a. tab completion), this would be a splendid addition which I must look into.
This new release also fixes an issue found by Dave Minter, thanks for the feedback Dave, hopefully you will find things a bit more bulletproof now.
Please keep your thoughts and ideas rolling in, cheers.