Download SimpleTick 0.1
Install is easy as pie. Just extract the zip file to it's own folder, your desktop, whatever. Any computer these days should be able to do this by default. Then just run the program and tada! There it goes. No installer, no admin privileges, just runs. Uninstall is just as easy, delete the three files.
OS: Windows (probably Linux too w/Wine or Mono)
Software: .net framework (2.0 or higher should work, untested).
Now I know some of you will criticize me for my choice of language (C#) and platform (.NET/Windows). Being an ex-mac/linux user I feel your pain. So I promise to a.) make the code open source eventually and b.) rewrite it cross-platform for all to enjoy.
As for what it does, I wanted to keep it really simple. Here's the featurelist as of now:
+Tabata-based Timer (customizable to a degree)
So alrighty, try it out and see what you think. Constructive criticism and feature requests are always welcome, but remember I will be doing a rewrite sometime in the future so some requests may have to wait.