Windows Phone Airsoft App
The app has a full set of calculators and converters
"FPS to M/S to Joule" And back again
Battery charge time calculator
Gear set Ratio calculator
Rate of Fire Calculator
It has a Rate Of Fire tester - No hardware needed, it uses the microphone.
The app also describes how to make your own Cronograph, to measure velocity of your Airsoft Hardball guns.
Guides and How-To
Another big part of the app is a guides / how-to section.
Angle of engagement, Gearbox assembly, Short Stroke, Mosfet, etc.
Detailed guides with Pictures.
In other words
A full Airsoft / Hardball / softgun app with everything you need for your hobby.
Airsoft, Hardball, Chronograph, Rate of fire, Calculator