Global - Cool Tools is a handy free app which adds nine functions to your Nokia Lumia 800 and 710.
Available from the Windows Marketplace, it provides: a stopwatch; countdown clock; flashlight and emergency strobe; ruler; accelerometer orientation; soundcheck; distance\weight\temperature converter; restaurant tip calculator; and dice.
Most of these are self-explanatory and if you find yourself using the app frequently, you can pin it to your home screen.
The flashlight turns your screen in to a white panel, which is useful to help you find your keys in the dark. It also has an “emergency strobe”, which flashes your screen red and white. It’s the only weakness of this app, as I don’t think it would be that powerful in a real emergency.
The accelerometer could be used as a rough spirit level to determine the slope of a surface. And the soundcheck helps you to set the various volumes for your phone’s incoming alerts.