Sitting here with Ron talking about it. This actually arose from the fact that I get my paycheck based on the fiat-average over a span of time. E.g. if my paycheck is 1 dollar / day, and I want to know how much I am to be paid for the last week, I would need to measure the weighted average of the USD exchange rate over the last week multiplied by 7.

I'm expecting the user to input:
Her local currency
Her salary in local currency per day
Beginning and ending dates

The user gets:
Her paycheck in BTC, based on the fiat-average exchange rate of the relevant dates.