From More Computer:
Provides a convenient Enriched Air Nitrox blending calculator on your iPhone. This calculator can be used at your air station to provide the information you need to fill a Nitrox tank from any existing mix (or empty).
The calculator also provides a bleed down calculator to easily change an existing mix with minimum waste oxygen. Convenience calculations are also available for Equivalent Air Depth, Maximum Operating Depth at various oxygen partial pressures and to figure out the best mix for a planned depth, and oxygen partial pressure.