I love Tomboy, it is a great program, but it is missing a little bit what I need.

Let's say I want to clean my room (yes, lame example, but can't create something better), so I write me a note "Clean a room" and that note is shown every 15 minutes let's say until I delete that note or mark it is finished.

Or let's say I create a note that in two days there is my mother's birthday and it reminds me every 6 hours and stop reminding me it in two days.

Well, I search for similar programs, do you know any?

Thank you very much and sorry for my English.