I actually thought that pizza delivery is a great fit, the people that have to do this job are putting in a lot of miles and gas just to deliver a couple of boxes for most deliveries. I just like the Taxi coloring idea to try first.
I think the next best commercial application for the Elio is the Zip Cars. I'm sure most of those cars are single occupant only. The fleet has plenty of compacts now. Imagine the Elio's popularity if Zip Car could offer the Elio for half or 2/3 the price per mile or hour that they charge now for their compact cars.
I used to do a lot of international travel and in most countries I visited pizza was delivered on fleets of mopeds. If you can do it on a moped then the Elio should be even better.
I heard a radio ad for Zip cars just the other day and also thought this would be a great idea for them. Inexpensive little car that sips fuel is great since fuel is included in the zip car fee.
I believe Elio could also be a good fit for a cheap rental car in general. While traveling for business I was frequently the only person in the rental car and only had to carry a bag or two from the airport to the hotel.