Have something to do with Chemistry or Physics? Check out PocketChemistry!

Why free? I needed a program like this, and it turned out I had to pay. I agree you should pay for complex software, but it takes less than a day for something like this. I wrote it for myself and decided I could share it with others. So here it is, for free.

Installation. Run the file you download. The program will place a shortcut in the start menu for quick access. It will also tell you how to set up a hardware key. P.S. You need to have 6 kb RAM free on your device. That's all it takes.

Usage. Whenever you want to switch off the screen, use the shortcut or the hardware key you've set up. You can turn the screen back on by pressing the Up key on the device.

Disclaimer. As I said, less than a day for the whole thing, so don't expect much. Things like a shortcut in Today, or a timer, or whatever aren't (and won't be) implemented. If I ever do that, it won't be freeware anymore.