PalmPilot Convertor Pro 4.0
the author of this app says:
This program has 37 different categories and holds nearly 500 different conversion units.
Convert length, area, weight, flow, power, volume, time, angle, pressure, velocity, temperature, force, density, energy, acceleration, scientific prefixes, illuminance and much more.
Categories and factors are fully editable.
PalmPilot Convertor Pro has eight empty categories for customization.