So the input is origin and destination, and the output is travel time? I doubt whether Google is going to provide the data for free. Let me see what services are available on the market.
I think output should be travel time with traffic information in real time for example accidents, road works abit like google maps which gives you full details, this app would be ideal in the morning when leaving for work with notification of any delays to work.
I'm curious - do you usually drive to work or take public transport?