In Moodle servers with a hig activity, if the students use the spell-check a lot, since each spell check involves the execution of the "aspell" command it can slow down the overall server performance. Each execution means the creation of a process, the loading into the memory of the desired language ffile, the parse of the text... and this is resource consumming. To solve this problem Jordi Martinez and I implemented a webservice that allows you to move the aspell to another server.
As a easter-egg this webservice logs the spellchecking sessions and has a lilte stats utility ...
I discontinued my work in moodle spellchek a year ago, so maybe somebody can take over the project.
You can find all the code and documentation here:
http://lafarga.upc.edu/projects/myspeller/
I hope you like it.
Marc