Build me an App

We manufacturer truck-trailers (refer [login to view URL]) for the road freight industry in Africa. We want to offer a free application to the industry that has a payload calculator and bridge formula calculator. Maybe some other features to add at a later stage like maintenance, tips etc. Inputs from user would be various truck models available in the market with our main trailer range and users can pair a truck with choice of trailer to estimate payload within South Africa. As we go along would like to add other jurisdictions like Zambia, Tanzania etc. We will supply necessary information on trucks, trailers and methods to calculate payloads. Also want option for user to customise their own rig (e.g. different truck with different trailer weights).