Here’s a small java program I did a while back. I know it works on Windows XP/Vista and Windows 7. I haven’t tested it on Linux or Mac yet.
Basically it keeps track of things you have completed, like a reverse todo list app. It doesn’t keep track of things you need to do, but rather what you have already done.
I took the twitter limit of 140 chars and implemented it in iDid as well. So the task description has to be less than 140 chars as well.
You can download the program here. Send me a msg/email if it doesn’t work on your OS.