Mileage Tracking and Reporting System

I'm trying to think of a way to track mileage efficiently, but I am unsure of how to approach it.

On the one side, I could use Google Cloud services and build a custom-built solution and on the other side I could simply use an existing tool/app that already does this and then just obtain the information using their API and this might might even be more accurate. Why re-invent the wheel?

What would you suggest?

a.) Build it from scratch and use Google Cloud (1 – 2 months)

b.) Use an existing solution (2 – 3 weeks)