Which gave me the Idea. Spare parts and service for consumer durables could be an ideal online business. Unlike most ecommerce that have a difficult relationship with consumer durable principals ( Channel conflict, price cuts etc.), most principals would be happy if a third party stocked, shipped and services spare parts that durables need. It is a part of their business they are not interested in. Also by definition, spare parts are needed occasionally so national level aggregation is of value.
I would start with mobiles, fridges, TVs, AC's - high value durables.